Improvements relating to the Treatment of Ores Containing Blende or Zinc in Association with Gold, Silver, Lead, Copper, Antimony, Sulphur, and other Metals or Metalloids, and to Apparatus therefor.
Year: 1892

page_text: Date of Application, 4th May, 1892
Complete Specification Left, 4th Feb., 1893-Accepted, 4th Aug., 1893
PROVISIONAL SPECIFICATION.
Improvements relating to the Treatment of Ores Containing Blende
or Zinc in Association with Gold, Silver, Lead, Copper, Antimony,
Sulphur, and other Metals or Metalloids, and to Apparatus
therefor.
We, HENRY RYAN Lewis, of 7, Drapers' Gardens, in the City of London,
Mining Engineer and Metallurgist, and CHARLES GELSTHARP, of 86, Addison
Road, Heaton, Newcastle-on-Tyne, in the County of Northumberland, Metallurgist,
do hereby declare the nature of this invention to be as follows:-
The object of our invention is to provide in a more simple and efficient manner
than heretofore, for the separation or extraction of zinc from ores in which the
same is mixed or associated with other metals, such as lead, silver, copper or gold,
and with metalloids, such as sulphur.
Our said invention comprises an improved method of accomplishing this result,
by first converting the sulphide of zinc contained in the ores into soluble sulphate
of zinc, and then dissolving or washing out the said sulphate of zinc and obtaining
metallic zinc from the solution thereof by electrolysis as hereinafter mentioned.
In carrying our said invention into practice, we first crush or reduce the ore
containing the mixed metals to a fine state by any of the methods usually
employed for such reduction, and we then roast the said ore at a low and properly
regulated temperature, so as to convert the sulphide of zinc contained in the said
ore into a soluble sulphate. In the roasting or calcination of the said ores, we
prefer to employ furnaces of the kind or class described in the Provisional Specifi-
cation accompanying our application for Letters Patent dated 5th April 1892
No. 6567, that is to say, furnaces in which there are a number of horizontal beds or
shelves placed one above another and so arranged that the hot gases from the upper
shelves may be conveyed under the lower shelves for the purpose of heating the
ore thereon. When the ore contains sufficient sulphur, the burning of the sulphur
keeps up the heat of the furnace when once started. When the ores do not contain
sufficient sulphur for this purpose, we keep the furnace hot by burning coal, coke,
wood or other solid, gaseous or liquid fuel beneath the bottom shelf or bed of the
furnace. Sulphuric acid and sulphur are obtained or recovered from the gases and
vapours given off in the roasting, which gases or vapours are conducted into a con-
denser or vitriol chamber. In the roasting or calcination of the ores, part of the
metallic contents may be volatilized, but we recover the same by condensation in
suitable condensers attached to the improved or other calcining furnace. For this
purpose, we find it advantageous to connect the improved calcining furnace, or
other furnace that may be employed for the calcination of the ores, by suitable
Blues, with a condenser or condensers filled with hollow brickwork and coke, and
through which a current of water is kept percolating or falling; all the metallic
fumes or vapours in the gases evolved by the calcination of the ores are passed
through the said condenser or condensers; any of the metals that may have been
volatilized in the roasting or calcining of the ores will, therefore, be contained in
the acid liquors produced and fumes deposited in the condenser or condensers; the
acid liquors are used for the purpose of leaching the roasted ore, the metals which
they contain being recovered along with the other metals contained in the ore.
The calcination of the ore as above mentioned may be effected in any of the
well-known caleining furnaces; we prefer, however, to conduct this operation with-
out bringing the ore into direct contact with the gases from the fire, so that we may
collect the sulphurous acid given off during the calcination, and may use the same

page_text: for the preparation of sulphuric acid. For this purpose, we connect the furnace
by means of suitable flues with sulphuric acid chambers, or we pass the sulphuric
acid over hot peroxide of iron to obtain sulphuric acid; or we pass the sulphurous
acid vapours through hot coke or carbonaceous matter and then through hot
checkered brickwork to obtain sulphur. We then dissolve or wash out with water,
the soluble sulphate of zinc contained in the roasted ore, or we may employ in the
dissolving or washing-out process dilute sulphuric acid, consisting of about three
parts of water to one of concentrated acid, or a sufficient quantity to unite with
any oxide of zinc in the said roasted ore and form soluble sulphate of zinc. We
then pass a current of electricity through the solution thus obtained, by which
means the zinc is deposited in a state of purity and free from matters with which
this metal is associated in commercial zinc or spelter. In treating the said solution
by electrolysis, we place a porous partition in the vat or vats, or tank or tanks,
containing the said solution, and on one side of the partition we place a quantity of
lime, limestone or other alkaline earth or alkali, or carbonates of the same, capable
of neutralizing the acid as it is liberated from the zinc. And to the sulphate of
zinc solution, where necessary, we add a small quantity of carbonate of soda or
maguesia to render the solution alkaline before passing an electric current through
it, and if, at any time during the passing of the electric current, the zinc ceases to
deposit freely, we add a further quantity of carbonate of soda or magnesia so as to
keep the bath alkaline. We place the negative poles or cathodes in the sulphate
of zinc solution on one side of the partition, and the positive poles or anodes in the
lime, limestone, alkaline earth or alkali on the other side of the partition. By the
action of the electric current, the zinc is all completely deposited in a state of purity
on one side of the partition, and the sulphate of lime or other sulphate remains on
the other side of the said partition in the said vat, vats, tank or tanks. If, on
testing the zinc solution, we find that some of the silver contained in the said ore
has been dissolved or washed out with the soluble sulphate of zinc, we add to the
said solution, before passing the electric current through it, a small quantity of
chloride of zinc or other chloride, or metallic zinc, to precipitate the silver, which
is recovered before the electro-deposition of the zinc. We find that, when the ore
is properly roasted, nearly the whole of the copper is rendered soluble, so that it
leaches out along with the zinc; and, on passing the electric current through the
solution, the copper is all deposited first, so that it may be separated in this manner;
or the copper may be first precipitated with old iron, or with zinc powder, and
the zinc then be deposited by the electric current.
After washing out or dissolving the soluble sulphate of zinc contained in the
roasted ore, we smelt the residue in water-jacketed or other furnaces, with a suitable
mixture or burden, to produce a matte containing lead, silver, copper, and other
metals, which can be separated by any well-known process.
Should the said ores contain an excess of zinc, that is to say, more zinc than can
be converted into sulphate of zinc by the sulphur contained in the ore in the roast-
ing thereof, or should there be any difficulty in converting the zinc contained in the
said ores into a soluble sulphate of zinc, we proceed as follows:-When the said
ores have been roasted for some time in our said improved furnace or in an ordinary
calcining furnace, we add to the ore, while in the furnace, a small quantity of
sulphate of iron or other sulphate, and then continue the roasting until the zinc is
soluble there will be some sulphate of iron left in the solution after the zinc is
deposited, which sulphate we sometimes recover and use for this purpose; when
necessary, we place the roasted ore in a vat, vats, tank or tanks divided by means
of vertical pervious or porous walls or partitions. We place the roasted or calcined
ore on one side of the partition or partitions and cover it with water, and we place
water or a suitable solution on the other side. We place in the ore one or more
positive poles or anodes, and in the water or solution we place negative poles or
cathodes, and theu pass a current of electricity through the ore and solution until
all the zinc is extracted and deposited on the negative pole.
The residue of the roasted ore we smelt in water-jacketed or other furnaces to

page_text: produce a matte containing lead, silver, copper, and other metals, which can be
separated by any of the well-known processes.
If the ore does not contain sufficient lead, we add a small quantity of ore con-
taining sulphides, und then smelt to produce a matte containing the lead, gold,
silver and other metals. Or we roast the silicious residue with salt, and then leach
out the gold and silver and precipitate them from the solutions by adding a small
quantity of the zinc powder, or by other well-known methods. Or we treat the
residue with chlorine and with an electric current, when necessary, to extract the
gold and silver.
Dated this 4th day of May 1892
D. YOUNG & Co.,
11 & 12, Southampton Buildings, London, W.C.,
Agents for the Applicants.
COMPLETE SPECIFICATION.
Improvements relating to the Treatment of Ores Containing Blende
or Zinc in Association with Gold, Silver, Lead, Copper, Antimony,
Sulphur, and other Metals or Metalloids, and to Apparatus
therefor.
We, HENRY RYAN LEWIS, of 7, Drapers' Gardens, in the City of London,
Mining Engineer and Metallurgist, and CHARLES GELSTHARP, of 86, Addison
Road, Heaton, Newcastle-on-Tyne, in the County of Northumberland, Metallurgist,
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 :-
The object of our invention is to provide in a more simple and efficient manner
than heretofore for the separation or extraction of zinc from ores in which the same
is mixed with other metals, such as gold, silver, lead, copper, antimony or bismuth,
and with metalloids, such as sulphur, so that the precious or more valuable metals
may be readily obtained from the residue of the ores free from zinc, the zinc,
moreover, being recovered in a metallic form.
Our said invention comprises an improved method or process of accomplishing
this result, by first converting the sulphide of zinc contained in the ores into soluble
sulphate of zinc, and then dissolving or washing out the said sulphate of zinc and
obtaining metallic zinc from the solution thereof by electrolysis as hereinafter
described. A part of this improved method is also applicable for obtaining
metallic zinc in a similar manner from sulphate of zinc formed by other processes.
Our said invention also comprises an improved apparatus hereinafter described
for obtaining metallic zinc from sulphate of zinc, or from ores containing blende or
zinc, by electrolysis.
In separating or extracting zinc from ores according to our said invention, we
proceed as follows, viz. :-We first crush or reduce the ore containing the mixed
metals, to a fine state of division, by any of the methods usually employed for such
reduction, and we then roast the said ore at a low and properly regulated
temperature, so as to convert the sulphide of zinc contained therein into a soluble
sulphate. The ore for this purpose should be maintained at a constant or uniform
temperature of from 300 to 700 degrees Centigrade for a period of from 36 to 72 hours,
according to the quality or nature of the ore under treatment.
In the roasting or calcination of the said ores, we prefer to employ furnaces or
apparatus of the kind or class described in the Specification accompanying our
application for Letters Patent dated 5th April, 1892, No. 6567, that is to say:-
Furnaces in which there are a number of horizontal beds or shelves placed one
above another, and so arranged that the hot gases from the upper shelves may be
conveyed under the lower shelves for the purpose of heating or maintaining the
heat of the ore thereon. When the ore contains sufficient sulphur, the burning of

page_text: the sulphur keeps up the heat of the furnace when once started, and maintains a
suitable temperature therein for the conversion of the sulphide into sulphate. When
the ores do not contain sufficient sulphur for this purpose, we keep the furnace hot
by burning coal, coke, wood, or other solid, gaseous or liquid fuel beneath the
bottom shelf or bed of the furnace. Or we construct a fire-grate under the lower
shelf, and burn on the said grate, coal, coke, wood, or other solid, gaseous or liquid
fuel, to maintain the temperature required. Or we make the horizontal shelves
hollow, and pass the heat produced through the same. Or we burn gaseous or
liquid fuel in the hollow space in the horizontal shelves, to maintain the temperature
required.
Sulphuric acid and sulphur are obtained or recovered from the gases or vapours
given off in the roasting, which gases or vapours are conducted into a vitriol
chamber or into a condenser or condensers, substantially as described in our
aforesaid former Specification. Or we pass the sulphurous acid over hot peroxide
of iron to obtain sulphuric acid; or we pass the sulphurous acid vapours through
hot coke or carbonaceous matter, and then through hot chequered brickwork to
obtain sulphur, as described in our said former Specification.
In the roasting or calcination of the ores, part of the metallic contents may be
volatilized, but we recover the same by condensation in suitable condensers attached
to the improved or other calcining furnace substantially as described in our said former
Specification. For this purpose, we find it advantageous to connect the improved
calcining furnace or other furnace that may be employed for the calcination of the
ores, by suitable flues, with a vitriol chamber and, if necessary, with other collecting
chambers, and with a condenser or condensers filled with hollow brickwork and
coke, and through which a current of water is kept percolating or falling. All the
metallic fumes or vapours in the gases evolved by the calcination of the ores are
passed through the said condenser or condensers. Any of the metals that may have
been volatilized in the roasting or calcining of the ores will, therefore, be contained
in the acid liquors produced and fumes deposited in the condenser or condensers.
The said liquors are used for the purpose of leaching the roasted ore, the metals
which they contain being recovered in addition to all the other metals contained
in the ore.
The calcination of the ore as above described may be effected in any of the
well-known calcining furnaces. We prefer, however, to conduct this operation as
above set forth without bringing the ore into direct contact with the gases from the
fire, so that we may collect the sulphurous acid given off during the calcination,
and may use the same for the preparation of sulphuric acid, and may also, as above
stated, recover any metals that may be volatilized.
The roasted or calcined ore we then place in suitable vats or tanks, and dissolve
or wash out the sulphate of zinc therein, for which purpose we use water and the
acid liquor produced by conveying the gases or metals evolved from the ore on the
lower shelves of the improved furnace, through the chambers or condensers as
herein before described; or we use dilute sulphuric acid or sulphurous acid in
sufficient quantity to unite with any oxide of zinc in the said roasted ores, to form
soluble sulphates or sulphites of zinc. We then pass a current of electricity as
hereinafter described through the solution thus obtained, by which means the zinc
is deposited in a state of purity.
In our improved method or process of treating the solution thus obtained or of
obtaining metallic zinc from other sulphate of zinc solutions, we provide for the
taking up or neutralization of the sulphuric acid as fast as it is liberated from the
zinc by the electric current. For this purpose, we use lime, limestone or other
alkaline earth or alkali or other compounds of calcium, barium or lead, so placed
in the compartments of the depositing vat or tank which contain the positive poles
or anodes, that the sulphuric acid will be liberated from the zinc in actual contact
with or in close proximity to the lime or its equivalent. The lime, limestone, or
other alkaline earth or alkali, or equivalent substance, when thus arranged, greatly
assists the current in separating the sulphuric acid from the zinc by combining with

page_text: the acid, and also prevents the acid from coming into contact with, or attacking or
dissolving the deposited zinc.
Our improved apparatus for obtaining metallic zinc from sulphate of zinc or
from ores containing blende or zinc, comprises suitable vats or tanks intended for
holding the sulphate of zinc solutions, or the ore as the case may be, and in which
are fixed either vertically or horizontally one or more porous partitions. We place
on one side of the partitions the positive poles or anodes, which may be made of
lead, or carbon, or of other suitable metal, and which are connected with a dynamo-
electric machine or other source of electricity; and we place on the other side of
the partitions the negative poles or cathodes, which may be made of sheets or plates
of zinc or of other suitable metal and which are also connected with the dynamo-
electric machine or other source of electricity.
In using our apparatus for the treatment of sulphate of zinc solutions, we place
in the said vats or tanks in the compartments in which are fixed the positive poles
or anodes, a quantity of water and lime, limestone or other alkaline earth, or alkali,
or carbonates of the same, or other compounds containing calcium, barium or lead,
capable of neutralising the sulphuric acid as quickly as it is liberated from the zinc.
We fill up the compartments of the vats on the other side of the partitions and in
which are fixed the negative poles or cathodes, with sulphate of zinc solution, and
to this sulphate of zinc solution, when necessary, we add a small quantity of
carbonate of soda or magnesia or other alkali to render the solution neutral or
slightly alkaline, and we pass the electric current through the said solution. If,
at any time during the passage of the electric current, the zinc ceases to deposit
freely, we add a further quantity of carbonate of soda or magnesia or other alkali,
to render the solution neutral or slightly alkaline. By the action of the electric
current, the zinc is all quickly and completely deposited in a state of purity on one
side of the partitions upon or adjacent to the negative poles, while the sulphuric
acid combines with the lime or other alkaline earth or alkali or equivalent
substance to form sulphates, which remain on the other side of the partitions.
After the zinc is all deposited from the solution, we draw off the exhausted solution
and use it for leaching fresh roasted orc. The deposited zinc, after washing, is
ready for use, and is either packed into barrels or melted down and run into ingots.
The lime or limestone or other alkaline earth, when all converted into sulphate, is
taken out of the vats (and may be used, after burning, for plaster of paris, or for
building purposes, or as manure) and fresh lime or limestone or other alkaline
earth or alkali is then added and a fresh solution of sulphate of zinc is also added
to the vats and the electric current is passed through as before, taking care at all
times to keep sufficient lime or the like in contact with or in close proximity to the
positive pole or anode to neutralize and take up the sulphuric acid as fast as it is
liberated from the zinc. To make this action more complete, when necessary, we
attach the positive poles or anodes to a wheel or to arms, which we fix vertically
or horizontally in that compartment of the vat in which the lime or equivalent
substance is placed, and we cause the said wheel or arms to revolve while the
electric current is passing through the poles and through the solution.
If, on testing the zinc solution, we find that some of the silver contained in the
said ores has been dissolved or washed out with the soluble sulphate of zinc, wo
add to the said solution, before passing the electric current through it, a small
quantity of chloride of zinc, or other chloride or metallic zinc, to precipitate the
silver, which is thus recovered before the electro-deposition of the zinc. We find
that, when the ores are properly roasted in our improved furnace, nearly the whole
of the copper is rendered soluble, so that it leaches out with the zinc, and, on
passing the electric current through the solution the copper is all deposited first,
so that it may be separated in this manner, or the copper may be first precipitated
with old iron or zinc powder, and then the zine deposited by the electric current.
There will be some sulphates left in the solution after the zinc is deposited; these
sulphates we sometimes recover and use in any desired manner.
If at any time, we find any iron in the deposited zinc, we add to the solution of

page_text: sulphate of zinc, before running the same into the depositing vats, a small quantity
of bleaching powder, or chloride of lime or chlorine, which precipitates all the iron
as ferric oxide; this ferric oxide we allow to settle, and we then draw off the clear
solution of sulphate of zinc into the depositing vats. We are thus enabled to
obtain, by the aid of electrolysis in the manner above described, zinc absolutely
free from iron.
When the ores or compounds are of such a nature or quality that the zinc will
not leach or wash freely out of the ores after roasting, we treat the ore itself, either
before or after roasting, in the depositing vats or tanks divided by means of
vertical or horizontal porous partitions or walls as above described. We place the
ore on one side of the partitions and cover it with water or dilute sulphuric acid or
solution of sulphate of zinc, and we place water or a solution of sulphate of zinc
or a previously exhausted solution on the other side. We place in the ore one or
more positive poles or anodes which may be made of carbon or lead or of other
suitable metal, and may be attached to wooden wheels or arms, which may be
caused to revolve in the ore; and we place the negative poles or cathodes in the
water or solution of sulphate of zinc or previously exhausted solution, and then
pass a current of electricity through the ore and solution until all the zinc is
extracted from the ore and deposited on the negative poles or cathodes. The
deposited zinc is then, after washing, packed into casks or melted and run into
ingots.
The residue left after the zinc is extracted from the ore as just above described,
or the residue left after leaching or washing the roasted ore with water or dilute
acid as hereinbefore described, we smelt in water-jacket or other furnaces, and
thus produce bullion or matte containing all the lead, silver, gold and copper,
which can then be separated by any well-known process.
If the residues left after
the leaching of the ore, or other treatment thereof as above described, do not
contain sufficient lead, we add to them a small quantity of lead or a small quantity
of ore containing sulphides of lead, and then smelt them, to produce either bullion
or matte, containing all the silver, gold, lead or copper, which may then be
separated by any well-known process. Or we roast the silicious residues with salt,
and then leach out the gold and silver and precipitate them from the solutions by
adding a small quantity of the zinc powder or by other well-known methods. Or
we treat the residue with chlorine and with an electric current to extract the gold
and silver.
Should the ores or compounds contain an excess of zinc, that is to say, more
zine than can, in the roasting of the ore, be converted into sulphate of zinc by the
sulphur contained in the ore, or should the ores be of such a nature that it is
difficult to convert the zinc contained therein into soluble sulphate, we proceed as
follows: When the said ores have been roasted for some time in the improved
furnace, or in any well-known and suitable calcining furnace, we add to the ores,
while in the furnace, a small quantity of sulphate of iron or other sulphate or
sulphide, and then continue the roasting until the zinc is all or nearly all converted
into soluble sulphate of zinc.
In the accompanying drawing we have shewn our improved apparatus for
obtaining metallic zine from sulphate of zinc, or from ores containing blende
or zinc.
Figure 1 is a side elevation, partly in vertical section, of one form of our said
apparatus.
Figure 2 is a transverse section of the said apparatus on the line x, x, Figure 1.
Figure 3 is a transverse section of another form or modification of the said
apparatus, and
Figure 4 is a side elevation, partly in vertical section, illustrating a further
modification of our invention.
A, A are leaching tanks or vats for washing out the sulphate of zinc from the
roasted ores or compounds; B is the depositing vat; C is a tank for leaching ore,
or containing lime for more completely neutralising the acid contained in the liquor

page_text: from the depositing vat. a is a cock or valve and b a pipe for conveying the
sulphate of zinc solution to the depositing vat B. D is a tank for storing the
liquor from the tank C. E is an injector for lifting the said liquor from the low
to the high level through the pipes F, G.
H, H are the hoppers or bins for the supply of lime or the like, or of ore as the
case may be, to the vat B, through suitable valves or gates H¹.
J, Jare partitions dividing the vat B into a series of compartments, the
portions J, J of the said partitions being porous to permit the circulation or
flow of the sulphate of zinc solution and the passage of the electric current, and
the remaining portions of the said partitions being made of wood or other suitable
material, so that the solution will flow in the direction indicated by the arrows in
Figure 1.
P, P are the positive electrodes or anodes which are made of lead or carbon
plates or of other suitable metal. In the compartment containing these electrodes,
we place, in the position shown, the lime or equivalent substance for taking up or
neutralizing the sulphuric acid as it is liberated from the zinc. N, N are the
negative poles or cathodes, which are of zinc or carbon, or of other suitable metal.
K, K are valves for drawing off the liquor, when required, to empty the vat B.
L is a cock or overflow pipe for conveying liquor from the depositing vat into the
tank C. M, M are valves for drawing from the vat B either deposited zine (which
is in a fine crystalline state), sulphate of lime or exhausted ore. Q is a waggon
for receiving the zinc or sulphate of lime or exhausted ore.
The sulphate of zinc solution enters the depositing vat B through the cock a
and pipe and then passes through the porous partitions J', alternately through
the lime or equivalent substance placed in the compartments containing the
positive poles P', and through the compartments containing the negative
poles N, as indicated by the arrows, till it arrives at the cock or pipe L,
through which it passes into the tank C and through the ore or lime contained
therein, whence it is discharged into the tank D, or is raised by the injector E into
the tanks A; the liquor thus constantly circulates, and the acid is neutralized as
fast as it is liberated, by passing through the lime while the current is passing
through the solution. The zinc is deposited upon the negative poles and
accumulates in the spaces marked Z.
In using the apparatus for the treatment of the ores by electrolysis, we put the
ores in the compartments containing the positive poles or anodes, in place of the
lime or the like.
In some instances, we modify the apparatus by arranging the porous partitions
as shown in Figure 4, and we fill the compartments containing the positive poles or
anodes, with lime or other alkaline earth or alkali (or with ore as the case may be)
up to a higher level, as shown in this figure.
In the modification of our apparatus illustrated in Figure 3, porous partitions J
are arranged horizontally, and the plates forming the positive poles Pare
attached to suitable arms or to a wheel R fixed upon a vertical shaft S con-
nected by bevel gear-wheels with a suitable motor. By these means, the positive
poles or anodes are made to revolve in contact with the lime or the like, or with
the roasted ores as the case may be, while the electric current is passing through
the solution.
Moreover the lime, lime-stone, or other alkaline earth or alkali, or the roasted
ore as the case may be, can be agitated or kept in motion, so as to expose fresh
surfaces and cause the efficient circulation of the liquors.
The sulphuric acid liberated on one side of the porous partitions is retained in
combination with the lime, lime-stone or other alkaline earth or alkali or equivalent
substance, and thus prevented from acting on the deposited zinc.
By reason of the construction and arrangement of our improved apparatus as
herein before described, the sulphate of lime, or other sulphate, or the exhausted
ore, or the deposited zinc, may be withdrawn or discharged from the vats or tanks,

page_text: and fresh ore, lime, limestone, or other alkaline earth or alkali, added without
moving the poles, either cathodes or anodes.
We are aware that it is not new to roast or calcine ores containing blende or
zinc for the purpose of converting the sulphide of zinc into sulphate of zinc, but
in our improved method or process we accomplish the desired result more
economically and more completely than heretofore. In our improved method or
process, although a charge of from four to six tons of ore is put into the furnace or
apparatus, and the same weight drawn out every six to eight hours, the ore is
exposed to the properly regulated temperature for say sixty hours, and without
using extra fuel; so that the ores are much more completely oxidised than
heretofore, and the zinc is all converted into soluble sulphate.
We are also aware that it is not new to obtain metallic zine from sulphate of
zinc by electrolysis; but we are not aware that it has ever been proposed to bring
the sulphuric acid as it is liberated from the sulphate of zinc into contact with lime,
lime-stone, or other alkaline earth or alkali placed around or in close proximity
to the positive poles or anodes for the purpose of taking up or neutralising the
sulphuric acid as fast as it is liberated from the zinc by the electric current, or for
preventing the liberated sulphuric acid from coming in contact with or acting upon
the deposited zinc, or for assisting the current to separate the sulphuric acid from
the zinc.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we wish it understood that
we do not claim broadly or irrespectively of our improvements hereinbefore
described, the roasting or calcining of ores containing blende or zinc for the
purpose of converting the sulphide of zinc into sulphate of zinc; nor the treat-
ment of sulphate of zinc or of ores by electrolysis for the purpose of obtaining
metallic zinc; but we claim ;-
First. The herein described improved method or process of separating or
extracting zinc from ores containing blende or zinc associated with other
metals such as gold, silver, lead, copper and antimony and with metalloids such
as sulphur.
Second. In the treatment of sulphate of zinc by electrolysis to obtain metallic
zinc, the use of lime, lime-stone or other alkaline earth or alkali or other com-
pounds containing calcium, barium or lead, in contact with or in close proximity to
the positive poles or anodes, in the manner hereinbefore described, for the purposes
specified.
Third. The improved apparatus constructed and arranged substantially as
herein before described, with reference to the accompanying drawing, for obtaining
metallic zinc by electrolysis from sulphate of zinc, or from ores containing blende
or zinc.
Dated the 3rd day of February 1893.
D. YOUNG & Co.,
.11 & 12, Southampton Buildings, London, W.C.,
Agents for the Applicants.