An Improved Process of and Apparatus for Extracting Gold from its Ores and Compounds.
Year: 1897

page_text: Date of Application, 23rd Mar., 1897
Complete Specification Left, 17th Dec., 1897-Accepted, 12th Mar., 1898
PROVISIONAL SPECIFICATION.
An Improved Process of and Apparatus for Extracting Gold from its
Ores and Compounds.
We, HENRY RENNER CASSEL, of No. 26, West 115th Street, and BERTRAND
CHASE HINMAN, of No. 22, Cliff Street, both in the City, County and State of New
York, United States of America, Metallurgists, do hereby declare the nature of
this invention to be as follows:
This invention relates to a method of and means for economically extracting
gold from its ores and compounds by the use of bromine Bromine being a
volatile liquid, giving off noxious vapours which are deleterious to life and pro-
perty and which cause waste, it is of great importance to prevent the escape of
such vapors, and accordingly the present invention is carried out in such al
manner that the generation of noxious fumes is prevented. Moreover the bromine
solution is recovered in its initial condition for further and continuous use.
The said invention comprises, firstly: An improved method of, and means for
treating the ores by bromine solutions in vats or barrels and for recovering the
bromine solution in its initial state for continuous use, and secondly:.
:-an improved
method of and means for treating the ores by bromine in the nascent or active
state in open vats.
According to one method, we charge a storage tank, with a solution of an
alkali, such as sodium hydroxide, carbonate or its equivalent, and bromine to form
an alkaline bromine solution, by which is meant a solution of a bromine com-
pound of an alkaline base. If caustic soda is used, we take about one part of this
hydroxide dissolved in water for two parts of bromine, but the proportions may be
altered according to requirements. The characteristic property of this alkaline
bromine solution is that it does not even after a long time lose its solvent power in
open storage vessels, and that when its bromine is brought into a nascent or active
state while in intimate contact with the ore, it will rapidly dissolve the gold.
An open vat having a perforated bottom is charged with pulverized ore. Dilute
acid, such as sulphuric acid of about 10 degrees Beaume, is then admitted to said
vat and allowed to percolate through the ore so as to moisten the same thoroughly
and to render it acid. After the acid has percolated through the ore and the excess
has been discharged through a tap, the alkaline bromine solution is gradually
admitted into the vat in sufficient quantity to keep the ore submerged, the ore
remaining in a quiescent state. The solution in slowly percolating through the
moist acid ore is decomposed, the alkali combining with the acid and thus
liberating the bromine in the nascent or active state. This bromine being in
intimate contact with the ore exerts a powerful dissolving action upon the gold.
While the bromine is thus set free in the body of the ore, the ore itself remains
covered with a stratum of the alkaline bromine solution, so that no fumes can
possibly escape, and consequently open vats can be employed.
In those cases where the ore itself contains acids or acid salts, the strength of
the acid solution may be proportionately reduced or the acid omitted altogether.

page_text: The bromine solution is allowed to remain in contact with the ore for a time
sufficient to dissolve the gold.
If desired the operation may be reversed by first impregnating the ore with a
strong alkaline bromine solution and then adding the acid to set free the bromine
in the body of the ore while keeping the ore submerged.
The solution is allowed to run into a vaporising tank and water is poured over
the ore to thoroughly wash out the gold and bromine solution retained in the
interstices of the ore. The vaporising tank, will now contain the gold and the
free bromine in solution as well as the bromide salts formed during the operation.
To set this combined bromine free we now introduce into the solution, chlorine
which will displace the bromine from its combinations. Instead of chlorine any
other reagent capable of setting free the bromine may of course be employed.
All the bromine now being free, steam or air under pressure is injected into the
vaporizing tank so that the bromine is vaporized and is driven through a pipe into
a tower containing pebbles or other obstructive bodies. If air alone is employed,
the vaporizing process may be accelerated by heating the solution in the vaporiz-
ing tank.
Within. the tower, the bromine vapors meet a sub-divided stream of a solution
of an alkali such as sodium hydroxide, or carbonate or its equivalent, of regulated
quantity and strength admitted thereto, and the two combine to form a fresh
body of alkaline bromine solution, which runs from the tower into the storage
tank, from whence it is admitted into the vat to treat a fresh charge of ore as
above described.
In lieu of a single tower which has the disadvantage of producing a bromine
solution of variable strength, it is preferable to employ two or more towers with
intermediate receiving tanks arranged in steps. Any bromine passing through
the first tower unabsorbed is absorbed in the second or remaining towers as the
case may be. The intermediate tanks are arranged between the towers and each
tank receives the partly saturated alkali solution from the tower above and
discharges such solution into the tower below.
It will be seen that as the bromine is employed again for continuous use and is
put into its initial state of solution, it is only necessary to mix bromine with the
alkali solution, in the storage tank, or in the vaporizing tank at the beginning of
the operation or when the slight losses that may in time occur, require to be
replaced.
After the bromine has been expelled from the vaporizing tank, the gold solution
is drawn off into a precipitating tank, where the gold is precipitated by hydrogen
sulphide or other means; the precipitate is then collected, calcined and melted
into ingots.
According to a modification the absorbing towers are replaced by a series of com-
municating absorbing tanks which may be arranged in steps, and which are charged
with the alkali solution. The bromine vapors from the vaporizing tank pass into
the alkaline solution in the lowermost tank, and any excess of bromine that may
escape from said tank is absorbed by the next tank in the series. The alkaline
bromine solution in the lowermost tank is drawn off into the storage tank and is
replaced by the weaker solutions from the other tanks in the series.
After
According to another method, the pulverized ore is charged into a rotating
barrel, and is treated therein with an aqueous solution of bromine in excess.
the barrel has been rotated for a sufficient length of time to dissolve the gold, the
rotation is arrested and water is injected into the barrel. This causes the dissolved
gold and the bromine as well as all other soluble bromide salts that may have
formed, to be forced through a filter into a receiving tank.
After the strong
solution of gold and bromine has been thus discharged the washing water is
delivered into another tank for a purpose hereinafter specified.
The combined bromine is then set free by chlorine or otherwise, as previously
described, and the contents of the tank are discharged into a vaporizing tower of
similar construction to that above referred to. Into the lower part of the

page_text: vaporizing tower, steam or hot air is admitted to heat the pebbles in the tower and
the solution which slowly trickles down between the pebbles in innumerable sub-
divided streamlets. By subdividing the solution in this manner a large surface is
exposed to the action of the steam or air. The bromine is thus vaporized and is
driven off, into an absorbing or condensing tower similar in construction to the
vaporizing tower. Here the vapors meet a stream of the wash water which con
stitutes the condensing medium and the vapours are condensed into an aqueous
bromine solution, the strength of which may be regulated by increasing or
diminishing the flow of the condensing solution.
From the condenser, the aqueous bromine solution is conveyed into a storage
tank, from whence it is led into the barrel, for dissolving a fresh charge of ore.
An alkaline solution may also be used in the above described arrangement
of towers.
The hot gold solution from which the bromine has been separated in the
vaporizing tower, is run into a receiving or precipitating tank, where the gold may
be precipitated and treated as before described.
The lower end of the vaporizing tower may be enlarged to receive the original
charge of bromine in starting the process, or the additional charges of bromine
when the same are required.
It will be seen that by our invention we provide for a continuous process of
extracting gold by bromine without losing practically any of the solvent or
creating any noxious vapors.
The bromine by being vaporized and brought into a state of solution in the
manner described is always under perfect control, and the solution is obtained in
its initial condition ready for further use upon a fresh charge of ore.
' בד
N 1007
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicants.
An Improved Process of and Apparatus for Extracting Gold from its
Ores and Compounds.
We, HENRY RENNER CASSEL, of No. 26, West 115th Street, and BERTRAND
CHASE HINMAN, of No. 22, Cliff Street, both in the City, County and State of New
York, United States of America, Metallurgists, 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 a method of and means for economically extracting gold
from its ores and compounds by the use of a bromine solution in such a manner
that the generation and escape of noxious bromine fumes are prevented, and the
bromine solution is recovered in its initial condition for further and continuous
use.
According to the said invention the ores are treated by a bromine solution,
which may
be either alkaline or otherwise, by an alkaline solution being meant a
solution obtained by mixing bromine of an alkali in suitable quantities.. If an
alkaline solution be employed the bromine is liberated therefrom in the nascent or
active state in contact with the ore and rapidly dissolves the gold therein.
After the extraction of the gold has ceased, the bromine in the solution is
driven off by steam or air, and is then re-absorbed in suitable apparatus so as to
obtain a solution similar to that initially used.
In order that the invention may be clearly understood and readily carried into

page_text: effect we will proceed to describe the same by aid of the accompanying diagram-
matic drawings, in which
Figure
is a vertical section of one form of apparatus for treating ores in an
open vat according to our invention, and for recovering the bromine in a single
tower.
Figure 2 illustrates a modified form of the said apparatus which we may employ if
desired, this modification having two recovery towers.
Figure 3 shows an arrangement in which the recovery towers are replaced by
tanks containing alkali solution.
Figure 4 shows an arrangement in which both the evaporation and recovery of
the bromine are carried out in towers.
Figure 5 illustrates an apparatus in which the ore is treated in revolving barrels
or cylinder and in which an ordinary aqueous solution of bromine may be used.
Referring to the arrangement shown in Figure 1, a is an open leaching vat
serving to contain the pulverized ore, and having at the bottom thereof a filter a¹.
b is a tank to contain the alkaline bromine solution above referred to, which
solution may be produced by mixing bromine with a solution of hydrate or
carbonate of sodium. If the former, viz. hydrate of sodium be used, one part
thereof may be mixed with two parts of bromine, but the proportions may be
varied considerably. Such a solution does not fume nor does it deteriorate by
contact with the air and can consequently be kept in open vats without trouble.
The addition of the bromine is conveniently effected by means of a funnel 6¹
having a lid or cover and an outlet valve, the former to prevent escape of bromine
vapours and the latter to control the discharge of the funnel.
The ore if not already acid in its nature, has added to it a dilute acid, such as
sulphuric acid of about 10 degrees Beaume. This acid is admitted from a tank c,
and is allowed to percolate through the ore so as to moisten the same thoroughly
After the acid has percolated through the ore in the vat a and the excess has been
discharged through a tap a², the alkaline bromine solution is gradually admitted
into the vat through a tap 62 in sufficient quantity to cover the ore, which latter
remains in a quiescent state all through the extraction process. The solution, in
slowly percolating downward through the moist acid ore, decomposed, and the
alkali combining with the acid, liberates the bromine in the nascent or active
state. This bromine being in intimate contact with the ore exerts a powerful
dissolving action upon the gold. While the bromine is thus set free in the body
of the ore, the ore itself remains covered with a stratum of the solution which has
not been affected by the acid, so that no fumes can possibly escape, and conse-
quently open vats can be employed.
The bromine solution may in some instances be admitted to the lower part of
the ore vat, thus producing an upward percolation. Under these circumstances
the solution gradually ascends through the ore and the bromide salts produced
form a stratum on the top of the liquid, thus preventing fumes from rising into
the air.
In those cases where the ore itself contains acids or acid salts, the strength of
the acid solution may be proportionately reduced or the acid may be omitted
altogether.
}
The bromine solution is allowed to remain in contact with the ore until the gold
is dissolved, or the percolation may be carried on continuously either upwards or
downwards the upward percolation being very suitable for slimy ores.
If desired the ore may be first impregnated with a strong alkaline bromine
solution, the acid being added afterwards to set free the bromine in the body of
the ore.
'
After the solution has dissolved all the gold it will, it is run off through the
filter bed and a valve-controlled outlet pipe a³ into a vaporising tank d, and water
is poured over the ore- to -thoroughly wash out any gold and bromine solution
retained in the interstices of the ore.

page_text: The tank d, will thus contain the gold and the free bromine in solution as well
as the bromine salts formed during the operation.
Chlorine contained in a cylinder d' is now introduced into the solution to
displace the bromine from its combinations, or instead of chlorine other reagents
capable of displacing bromine may be employed. After this, air under pressure is
forced into the tank d from a blower e through a pipe e¹ having a perforated
extremity e³, so that the bromine is vaporized and is driven off. The air charged
with the bromine. passes into a tower f through a pipe f. If air alone be
employed, the vaporizing process may be accelerated by heating the solution in
the vaporizing tank, but steam or a mixture of steam and air may be employed
if desired.
The tower fis charged with a mass of pebbles or other suitable material and is
connected with a tank g containing a dilute solution of caustic soda or other alkali.
This solution is led into the tower through a pipe g¹ and trickles down over the
material in the same.
The bromine vapors ascending the tower combine with the alkali to form a
fresh body of alkaline bromine solution, which runs from the tower through a
pipe into the storage tank b, whence if sufficiently strong it is run into the
vat a to treat a fresh charge of ore as above described, or if not sufficiently strong.
may be used again to absorb more bromine. A pipe fa is provided in the top of
the tower for the escape of air used to vaporize the bromine.
After the bromine has been expelled from the vaporizing tank d, the gold solu-
tion is drawn off through a pipe into a precipitating tank h, where the gold is
precipitated by hydrogen sulphide or other means. The precipitate is then
collected, treated in the ordinary manner and melted into ingots.
:
Referring now to the arrangement shown in Figure 2, f f are the two recovery
towers, which are so arranged that any unabsorbed bromine passing through the
first tower will enter the second tower f* by a pipe f and be absorbed in the
said tower, the air finally escaping by the pipe f³. The tank g, which contains.
fresh solution of alkali, communicates in this case by the pipe g¹ with the tower fx:
The alkali bromine solution formed in the tower
into an intermediate tank 6* and thence by a pipe f
strengthened by the bromine vapours in said tower,
storage tank b."
Suitable cocks are provided in the various pipes to regulate the
flow of solution through them.
passes through a pipe f**
to the tower f where it is
and finally passes into the
It will be seen that as the bromine is again and again re-converted into it's
initial state of solution, it is only necessary to add fresh bromine at the beginning
of the operation or when the slight losses that may in time occur, require to be..
replaced.
Obviously instead of only having two towers we may if desired have three or
more arranged consecutively in a similar manner.
Referring now. to the arrangement shown in Figure 3, in which the absorbing
towers are replaced by a series of absorbing tanks, indicate the said tanks
which are in this case arranged in steps, and which are charged with alkali
solution. The mixture of air and bromine vapours from the vaporizing tank d
passes through a pipe having a perforated extremity into the alkaline solution
in the lowermost tank i and in bubbling up through the said solution the bromine
is absorbed, and forms a fresh quantity of alkaline bromine solution. Any excess
of bromine that may escape absorption passes through a pipe 23 and is absorbed in
the next tank. The alkaline bromine solution in the lower tank i is drawn off
into the storage tank band is replaced by the weaker solution from the other
tank 2.
' ***
Referring now to the arrangement shown in Figure 4 in which towers are used
both for the evaporation and the recovery of the bromine solution in its initial
condition, fis as before the recovery tower, while d indicates the evaporation
tower. The solution after dissolving the gold in the leaching vats a of which
there may be two or more is run into the closed tank d, where any combined

page_text: bromine is displaced as above described. The solution containing the gold and
free bromine is allowed to flow slowly into the tower d through a sprayer d³. The
bromine is expelled by an air current introduced into the tower through a pipe e¹,
and the vapours are driven through a pipe d' leading from the closed top of the
tower d into the bottom of the recovery tower f. This latter tower is open on top
and is provided with a perforated sprinkling tray f6 into which alkaline solution
flows from a tank 9. and from which it is distributed into the tower in the form of
a fine shower.
The bromine vapours in ascending the tower f meet the dilute solution of alkali
and at once combine therewith.
The fresh alkaline bromine solution thus formed passes from the tower f. through
a pipe into the solution tank b, and if strong enough is again ready for use.
On the other hand the solution from which the bromine vapours have been
expelled, passes from the tower d through a pipe f* into the precipitating tank h,
in which the gold contained in the said solution may be precipitated.
In the arrangement shown in Figure 5 wherein an ordinary aqueous bromine
solution may be used, the pulverized ore is charged into a rotating barrel or
cylinder k, Figure 3, and is treated therein with an aqueous solution of bromine
in excess.
The barrel or cylinder is rotated by a toothed ring ¹ and a pinion driven by
a belt or otherwise, and is provided with a charging opening having a lid or
cover and also with valve-controlled nozzles 5. Suitable flexible connec-
tions and 9 are or may be provided for connecting the barrel or cylinder with
the other parts of the apparatus.
10 is a perforated tray or filter plate, provided with asbestos cloth or other
suitable material to retain the ore.
At the commencement of the process, the barrel or cylinder is brought into the
position shown, and after it has been charged with ore, a quantity of bromine
solution is run into it from the tank 6 by the pipe k connected therewith, the other
pipes and being at this time disconnected. The lid or cover is then closed
and the barrel is rotated for a sufficient length of time to dissolve the gold. The
rotation is then stopped, the pipes and are connected up and water is injected
into the barrel by means of a pump l. The solution containing the dissolved gold
is thus forced through the filter 10 and up a branched pipe m provided with
valves m² m². From this pipe the solution is discharged into the left hand tank d
of a pair of receiving tanks à d° arranged respectively above a vaporizing tower d
and an absorption tower f, the valve m¹ being at this time open and the valve m²
being closed.
After the said solution of gold and bromine has been thus discharged into the
tank d, the valve m¹ is closed, the valve m² is opened and a further quantity of
water is forced by the pump into the barrel or cylinder to wash out the last traces
of gold and bromine solution from the ore, this water being delivered into the
right hand tank do for the purpose hereinafter specified.
The combined bromine in the liquid contained in the tank d is next set free,
say by chlorine admitted from a cylinder d' as before, and the contents of the tank
are then slowly discharged into the vaporizing tower d. Into the lower part of
this vaporizing tower, steam is admitted by a pipe n from a boiler n' to the solution
which trickles down the tower. The bromine is thus vaporized and is driven off
through a pipe d' into the absorbing or condensing tower f.
Here the vapours
meet a stream of wash water from the tank d° and are absorbed thereby, thus again
forming an aqueous bromine solution, the strength of which may be regulated by
increasing or diminishing the flow of the condensing solution.
The filling material in the vapourizing tower & rests upon a plate or grid do
and the said tower may be enlarged at its lower part as at de, the enlarged portion
forming a receptacle in which the liquid trickling down the tower collects.
The hot gold solution from which the bromine has been separated is run from

page_text: the vapourizing tower into a precipitating tank h, where the gold may be pre-
cipitated and treated as before described.
The freshly formed aqueous bromine solution is conveyed from the absorbing
tower finto the storage tank b, whence as before stated it is led into the barrel k,.
for dissolving a fresh charge of ore.
It will be observed that suitable air outlet pipes o are provided on the tanks d d°
and b, these pipes serving to permit the air in the tanks to escape during filling
and being provided with water seals o¹.
Although in connection with this last arrangement or apparatus we have referred
more particularly to the employment of an aqueous bromine solution, yet we wish
it to be understood that an alkaline bromine solution may also be used instead of
a simple aqueous solution, thus admitting of either steam or air or both being used
to vapourize the bromine in the tower d*.
Our invention provides a continuous process of extracting gold by means of
bromine without losing practically any of the solvent or creating any noxious
vapours.
The bromine by being repeatedly vaporized and brought into a state of solution
in the manner described is always under perfect control, and the solution is obtained
in its initial condition ready for further use upon a fresh charge of ore.
It will be readily understood that the relative arrangement or disposition of the
various parts shown in the drawings can be modified as desired without departing
from the nature of our invention. For instance in the arrangement shown in
Figure 5, the towers, and also the receiving tanks d d°, may be situated below the
cylinder & so that the gold solution can flow into them by gravity.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is:-
1. In a process of extracting gold from its ores or compounds, dissolving the
gold by bromine liberated from an alkaline bromine solution, then expelling the
bromine in the form of vapour and recovering the vapour in the form of a solution
of the same nature as the one originally used, substantially as and for the purposes
specified.
2. In a process for extracting gold, dissolving the gold by bromine solution and
then recovering the bromine in the form of a similar solution to that with which
the ore was originally treated, substantially as described.
3. Treating auriferous ores or compounds first with acid and then with an
alkaline bromine solution, or first with the alkaline bromine solution and then
with acid, so as to form active bromine in intimate contact with the ore or com-
pound in the former case the escape of vapours being prevented by the stratum of
liquid above the ore or compound, substantially as and for the purpose specified.
4. The apparatus for extracting gold by means of bromine, constructed substan-
tially as described with reference to the accompanying drawings, for the purposes
specified.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicants.