Improvements in the Treatment of Zinc Bearing Ores and Zinc Bearing Products.
Year: 1895

page_text: Date of Application, 13th July, 1895
Complete Specification Left, 13th May, 1896-Accepted, 11th July, 1896
PROVISIONAL SPECIFICATION.
Improvements in the Treatment of Zinc Bearing Ores and
Zinc Bearing Products.
I, EDGAR ARTHUR ASHCROFT, of Himalaya, Thomas Street Broken Hill, in
the Colony of New South Wales, Electrical Engineer, do hereby declare the
nature of this invention to be as follows :―
This invention relates to improvements in the process of treating, zinc bearing
ores and products and particularly argentiferous zinc and lead sulphide ores by a
continuous cycle of operations consisting in leaching the oxidized ore or product
with a solution containing a ferric salt whereby iron is replaced by zinc extracted
from the ore and then subjecting the solution to double electrolysis whereby
metallic zinc is deposited and the leaching solution is regenerated for use again,
as described in the Specification of previous Letters Patent dated July 18th 1894,
No. 13,850.
}
The improvements forming the subject of the present application have for their
object the simplification and cheapening of the process and they relate, firstly, to
the composition of the working solutions; secondly, to the method of performing
the double electrolysis; and, thirdly, to the method of performing the leaching
operation.
In order that the present improvements and their bearing on the working of the
process may be fully understood, I will describe the process as a whole, reference
being had to the drawings accompanying and forming part of this specification,
wherein I have illustrated apparatus adapted for the practical application of
the improved process.
The ore, if it contain zinc sulphide, is first subjected to an oxidizing roast
whereby the zine sulphide is converted as far as possible to neutral or basic zinc
sulphate and zinc oxide, any lead sulphide contained also undergoing oxidation
more or less completely. In the case of ores or products containing zinc only in
the form of oxide, such roasting will be unnecessary.
The ore or product having been ground to extreme fineness (which may be done
either before or after roasting) is then subjected in properly proportioned quantity
to the action of a leaching solution containing ferric salt, as hereinafter specified,
the reaction between the finely ground ore or product and the solution being
promoted by maintaining the same in a constant state of agitation by stirring or
otherwise, this operation being continued for from half an hour to two hours and
the proportional quantity of ore and solution being so calculated that the reaction
with all the iron salt in the solution will be complete when so much zinc has been
extracted from the ore that the residue left is of good composition for subsequent
smelting. For instance with ores containing 30% of zinc, probably some 5%
would be allowed to remain in the residue, on account of the higher cost of total
extraction.
:
When the leaching is complete the solution is separated from the residues by
settling and decantation, or by filter-pressing, and the residues may be washed
with a small quantity of water which may be added to the solution to compensate
for loss by evaporation. The residues, containing the lead (in the form of
sulphates and oxides) the greater part of the silver, the gangue, and the iron which
has been precipitated from the solution in the form of ferric hydrate, are dried to
render them fit for smelting, for which purpose they may be made into bricks, with
or without the addition of quicklime, which will cause the mass to set much harder

page_text: and act as flux in the furnace; or the residues may, if desired, be heated to a dull
red heat to drive off the water of hydration from the ferric bydrate, agglomerate
the particles, and reduce the weight of the mass.
The solution, after being separated from the residues, may contain a small
quantity of silver, gold, copper, antimony, arsenic, manganese, alumina, silica, and
other foreign matters taken from the ore, also a small quantity of iron in the form
of soluble ferric hydrate, which foreign matters I prefer to remove as follows;-
before subjecting the solution to electrolysis.
The silver, gold, copper, antimony, and arsenic, together with any other metal
belonging to the same chemical group, may be precipitated by the action of metallic
zinc in the well known way.
Manganese may be removed by precipitating it from the boiling solution by
means of permanganate of potash and zinc oxide, according to the well known
reaction for the estimation of manganese in solution.
Alumina may similarly be removed by known chemical means, whilst the silica,
together with the soluble ferric hydrate, is readily precipitated by boiling the
solution, or will separate out after standing for a certain time.
It is not, however, found necessary, in practice, to remove all the above
impurities after every leaching operation. The manganese and alumina may be
allowed to remain until the quantity accumulated by the passage of the solution
over fresh batches of ore becomes inconvenient.
The solution having been brought to the condition indicated, is now to be treated
in the zinc electro-depositing plant where the zinc is recovered and the solution is
recharged with ferric salts so as to render it fit for use agaiu in the above described
operation of leaching.
The electro depositing plant consists essentially of a number of depositing vats
provided with metallic iron anodes and suitable cathodes (preferably zinc plates)
and a number of similar vats having anodes of insoluble material, such as carbon,
the total depositing capacity of the plates in the iron-anode vats being about
twice that of the carbon-anode vats. Diaphragms of porous material are placed
between the an de and the cathode plates so as to divide each vat into a number
of separate cells permitting the passage of the current without allowing the
intermingling of the liquids.
The form and arrangement of the depositing vats is not material, but one
arrangement which I have found suitable is shewn in the accompanying
drawings. Any suitable number of such sets of apparatus may be employed
and the connection and arrangement of the same may be varied to suit particular
conditions and requirements.
Figure 1 is a section of a leaching vat with stirrers.
Figure 2 shews the arrangement of electro depositing vats in a cascade and the
reservoirs.
Figure 3 is a general plan of the electrolysis plant.
.552
[
The circular leaching vat shewn in Figure 1 is provided with rotating stirrers
formed by a number of shoes or prongs fastened to a suitable frame carried
by a vertical shaft. The electro depositing vats are arranged in such a manner,
and with such pipe and trough connections between them, that a continual
circulation of solution in three separate stages of progress is maintained in the
system, the liquids being preferably circulated at sufficient speed to ensure a brisk
and continual motion at every part of the plates.
The depositing plant consists of a series of any number of electrolysis
vats A1, A2, A3, A', 'A', A5, A7, A8, A', preferably arranged as shewn in Figures 2
and 3, and a number of reservoirs B1, B2, B3, B4, B5, B. Each of the vats is
divided by diaphragms C of filter-cloth, or other suitable material, into a number
of compartments each of which has an inlet pipe D entering near the bottom and
an outlet pipe E discharging near the top.
Each of the vats A', A², A³, A', A', A, contains three iron anodes H and two
zinc cathodes K, while each of the vats A7, A8, A9, contains three carbon anodes M

page_text: and two zinc cathodes K. The electrical connections may be made in any suitable -
manner, all the plates in the same vat being connected in parallel and the plates of
successive vats being connected in series.
The reservoir B¹, has a number of exit pipes which discharge into the inlets of
the cathode compartments of the three upper vats A¹, A', and A'. The outlet
pipes of these compartments discharge into the inlets of the cathode compartments
of the vats A, A³, and A. The outlet pipes of these compartments discharge
into the inlets of the cathode compartments of the vats A³, A, and A³, and the
outlet pipes of these compartments discharge into the reservoir B².
The reservoir B³, has a number of exit pipes which discharge into the inlets of
the iron anode compartments of the vats A¹, and A. The outlet pipes of these
compartments discharge into the inlets of the iron anode compartments of the next
vats A, and A. The outlet pipes of these compartments discharge into the iron.
anode compartments of the vats A³, and A, and the outlet pipes of these com-
partments discharge into the reservoir B.
The reservoir B, has exit pipes which discharge into the inlets of the carbon
anode compartments of the vat A7. The outlet pipes of these compartments
discharge into the inlets of the carbon anode compartments of the vat A³. The.
outlet pipes of these compartments discharge into the inlets of the carbon anode:
compartiments of the vat A, and the outlet pipes of these compartments discharge
into the reservoir B6.
The pumps for raising the solutions from the reservoir B2, to the reservoir B³,
from the reservoir B, to the reservoir B³, as indicated by the arrows on Figure 3,
and from the reservoir B, to the leaching vat again, may be of any suitable
construction, and the reservoirs are preferably kept supplied from large storage
tanks (not shown).
The three batches of solution thus circulating consist of portions of the same
stock solution, each undergoing different stages of the operations. That circulating
past the zinc cathodes must be the solution of the zinc salts from which all iron
has been precipitated by the leaching operation and freed from impurities (if
necessary) as hereinbefore described. The solution circulating past the iron
anodes is a similar lot of solution which has previously circulated past the cathodes
and has thus become more or less depleted of its zinc. It is circulated past the
iron anodes until a sufficient quantity of iron has gone into solution as ferrous
salt. The solution circulating past the carbon anodes has been thus charged
with ferrous salt and it circulates past the carbon anodes until all the iron it
contains has been converted from the ferrous to the ferric state.
It will thus be observed that at each change of the solution the catholyte of
both iron and carbon anode vats becomes the anolyte of the iron anode vats;
the anolyte of the iron-anode vats becomes the anolyte of the carbon vats; the
anolyte of the carbon vats becomes the leaching solution; the leaching solution
after purifying, if necessary, becomes the zinc bearing solution and catholyte of
both iron and carbon anode vats, and so the cycle is complete.
The periods at which the changes of the solutions are made will depend upon
various circumstances, mainly upon the amount of the iron which it is found
convenient to impart to the solution and the amount of zine to remove therefrom
at each cycle.
It will be seen from the chemical reactions hereinafter described that for the
complete and continuous operation of this process two iron anode vats are required
to one carbon anode vat of equal depositing capacity. The process is continuous
and the solution passes through a cycle of operations thus-beginning with a
ferric solution containing more or less zinc and acting on the oxidized ore, the
operations are as follows:-First:-leaching whereby iron is thrown out of solution
and zinc substituted; second-circulation past the cathodes in the zinc electro
depositing plant where the excess of zinc is taken out; third :-circulation past
the iron anodes where ferrous salts are imparted to the solution ; fourth :-
circulation past the carbon anodes where the ferrous salts are oxidized to ferric
:-

page_text: salts and the solution thereby regenerated and ready to be again employed for
leaching.
Although I have found carbon anodes the most efficient and economical means
for oxidizing the ferrous salt solution to the ferric state, I would have it understood
that this may also be effected by known and suitable chemical reagents, such for
instance as chlorine gas, as will be well understood.
The use of iron anodes followed by the use of carbon anodes, besides affording
an economical means of obtaining iron salts in the solution for leaching the ore
with, prevents the setting-free-of-large-amounts of acids in the solution by
electrolysis (also the polarization accompanying the formation of such acids) and
which acids if allowed to remain and come in contact with cathode plates would
render the continuous deposition of the zinc impracticable. The useful purpose
of very materially reducing the energy required to decompose the zinc salts is
also served. The energy represented by the solution of the iron in the iron anode
vats and its higher oxidation in the carbon anode vats approaches very closely to
the total energy required to separate the equivalent amount of zinc at the
cathodes. For the foregoing reasons the production of zinc by this process is
unbampered by technical irregularities and requires very much less electrical
power than by any electrolysis process hitherto employed, and both the first cost
and cost of maintenance of the electrolysis plant are proportionately reduced.
For the soluble iron anodes cast, wrought, or scrap iron or steel may be used.
For the insoluble anodes gas retort carbon, prepared carbon, platinum, ferro-
silicon, or any other known and suitable substances may be employed. For the
diaphragms filter-cloth, or any of the known porous materials used for electrolysis,
may be employed. For the cathode plates almost any metal may be used, but I
prefer to employ sheets of zinc which may be melted up in a melting pot with the
deposits obtained or may be stripped and used again and again.
For the above described operations one of several solutions of different, though
analogous, compositions may be employed according to varying circumstances.
No. 1. Zinc chloride mixed with sodium, potassium, magnesium, or ammonium
sulphate.
No. 2. Zinc chloride mixed with sodium, potassium, magnesium, or ammonium
chloride.
No. 3. Zinc sulphate mixed with sodium, potassium, magnesium, or ammonium
sulphate.
The ferric salt required in each of the above solutions, in order to effect the
solution of the zinc, is generated in the electro depositing plant as herein
before described, the iron being first imparted by the iron anodes in the ferrous
state and subsequently oxidized to the ferric state.
The strength and the temperature at which the above solutions are employe
are not material and may vary between very wide limits. The solution which I
generally prefer to employ is the No. 1. solution. This solution contains from
10 to 50 grammes of zinc per litre as zinc chloride (which is, however, partially
displaced in the electrolysis by the iron salt as above mentioned) and from 20 to
50 grammes sodium sulphate.
The chemical reactions with this solution are as follows, and as they are
typical of the reactions with the other solutions it will be unnecessary to describe
the latter.
Electrolysis in two vats with iron anodes.
2 ZnCl, +2 Fe = 2 FeCl2 + 2 Zn.

page_text: The small quantities of sodium chloride so formed, together with the small
quantities of zinc sulphate (basic and neutral) formed in roasting the ore, will
further re-act to re-form sodium sulphate and zinc chloride on boiling the solution
which also throws out the soluble ferric hydrate and silica, as herein before
mentioned.
When the No. 2. solution is employed, sulphates not being present, any lead
chloride formed will remain unaltered and this salt being slightly soluble it may
be necessary to remove the lead from solution in any well known manner.
Dated this 13th day of July 1895.
A. M. & WM. CLARK,
53 Chancery Lane, London, Chartered Patent Agents.
COMPLETE SPECIFICATION.
Improvements in the Treatment of Zinc Bearing Ores and
Zinc Bearing Products.
I, EDGAR ARTHUR ASHCROFT formerly of Himalaya, Thomas Street, Broken
Hill, in the Colony of New South Wales, and at present of 34 Queen Street,
Melbourne, Victoria, Australia, Electrical Engineer, 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 process of treating zinc-hearing
ores and products and particularly argentiferous zinc and lead sulphide ores by a
continuous cycle of operations consisting in leaching the oxidized ore or product
with a solution containing a ferric salt whereby iron is replaced by zine extracted
from the ore and then subjecting the solution to double electrolysis whereby
metallic zinc is deposited and the leaching solution is regenerated for use again,
as described in the Specification of previous Letters Patent dated July 18th 1894,
No. 13,850.
The improvements forming the subject of the present application have for their
object the simplification and cheapening of the process and they relate, firstly,
to the composition of the working solutions; secondly, to the method of per-
forming the double electrolysis; and, thirdly, to the method of performing the
leaching operation.
In order that the present improvements and th. ir bearing on the working of
the process may be fully understood will describe the process as a whole,.
reference being had to the drawings accompanying and forming part of this
specification wherein I have illustrated apparatus adapted for the practical
application of the improved process.
The ore, if it contain zinc sulphide, is first subjected to an oxidizing roast
whereby the zinc sulphide is converted as far as possible to neutral or basic zinc
sulphate and zinc oxide, any lead sulphide contained also undergoing oxidation

page_text: more or less completely. In the case of ores or products containing zine only in
the form of oxide, such roasting will be unnecessary.
The ore or product having been ground to extreme fineness (which may be done
either before or after roasting) is then subjected in properly proportioned quantity
to the action of a leaching solution containing ferric salt as hereinafter specified,
the reaction between the finely ground ore or product and the solution being
promoted by maintaining the same in a constant state of agitation by stirring or
otherwise, this operation being continned for from half an hour to two hours and
the proportional quantity of ore and solution being so calculated that the reaction
with all the iron salt in the solution will be complete when so much zinc has been
extracted from the ore that the residue left is of good composition for
subsequent smelting. For instance with ores containing 30% of zinc, probably
some 5% would be allowed to remain in the residue on account of the higher cost
of total extraction.
When the leaching is complete the solution is separated from the residues by
settling and decantation, or by filter-pressing, and the residues may be washed
with a small quantity of water which may be added to the solution to compensate
for loss by evaporation. The residues containing the lead (in the form of sulphates
and oxides) the greater part of the silver, the gangue, and the iron which has been
precipitated from the solution in the form of ferric hydrate, are dried to render
then fit for smelting, for which purpose they may be made into bricks, with or
without the addition of quicklime, which will cause the mass to set much harder
and act as flux in the furnace; or the residues may, if desired, be heated to a dull
red heat to drive off the water of hydration from the ferric hydrate, agglomerate
the particles, and reduce the weight of the mass.
The solution after being separated from the residues may contain a small
quantity of silver, gold, copper, antimony, arsenic, manganese, alumina, silica, and
other foreign matters taken from the ore, also a small quantity of iron in the form
of soluble ferric hydrate, which foreign matters I prefer to remove as follows:-
before subjecting the solution to electrolysis.
The silver, copper, gold, antimony, and arsenic, together with any other metal
belonging to the same chemical group, may be precipitated by the action of metallic
zinc in the well known way.
Manganese may be removed by precipitating it from the boiling solution by
means of permanganate of potash and zinc oxide according to the well known
reaction for the estimation of manganese in solution.
Alumina may similarly be removed by known chemical means, whilst the silica,
together with the soluble ferric hydrate, is readily precipitated by boiling the
:solution or will separate out after standing for a certain time.
It is not, however, found necessary in practice to remove all the above impurities
after every leaching operation. The manganese and alumina may be allowed to
remain until the quantity accumulated by the passage of the solution over fresh
batches of ore becomes inconvenient.
The solution having been brought to the condition indicated is now to be
treated in the zinc electro-depositing plant where the zinc is recovered and the
solution is recharged with ferric salts so as to render it fit for use again in the
above described operation of leaching.
The electro-depositing plant consists essentially of a number of depositing vats
provided with metallic iron anodes and suitable cathodes (preferably zinc plates)
and a number of similar vats having anodes of insoluble material, such as carbon,
the total depositing capacity of the plates in the iron-anode vats being about
twice that of the carbon-anode vats. Diaphragms of porous material are placed
between the anode and the cathode plates so as to divide each vat into a number
of separate cells permitting the passage of the current without allowing the
intermingling of the liquids.
The form and arrangement of the depositing vats is not material, but one

page_text: 5
arrangement which I have found suitable is shewn in the accompanying
drawings. Any suitable number of such sets of apparatus may be employed
and the connection and arrangement of the same may be varied to suit particula
conditions and requirements.
Figure 1 is a section of a leaching vat with stirrers.
Figure 2 shews the arrangement of electro-depositing vats in a cascade and the
reservoirs.
Figure 3 is a general plan of the electrolysis plant.
The circular leaching vat shewn in Figure 1 is provided with rotating stirrers
formed by a number of shoes or prongs fastened to a suitable frame carried by
a vertical shaft. The electro-depositing vats are arranged in such a mauner, and
with such pipe and trough connections between them, that a continual circulation
of solution in three separate stages of progress is maintained in the system, the
liquids being preferably circulated at sufficient speed to
continual motion at every part of the plates.
ensure a brisk and
The depositing plant consists of a
vats A A A A A A A A A preferably arranged as shewn in Figures 2
series of any number of electrolysis
and 3 and a number of reservoirs B1 B2 B3 B4 B B. Each of the vats is divided
by diaphragms C of filter-cloth or other suitable material, into a number of com-
partments each of which has an inlet pipe D entering near the bottom and an.
outlet pipe E discharging near the top.
'
Each of the vats A¹ A2 A3 A4 A5 Aª contains three iron anodes H and two zinc
cathodes K while each of the vats A7 A8 A9 contains three carbon anodes M and
two zinc cathodes K. The electrical connections may be made in any suitable
manner, all the plates in the same vat being connected in parallel and the plates of
successive vats being connected in series.
The reservoir B has a number of exit pipes which discharge into the inlets of
the cathode compartments of the three upper vats A' A4 and A7. The outlet:
pipes of these compartments discharge into the inlets of the cathode compart-
ments of the vats A2 A and A8. The outlet pipes of these compartments
discharge into the inlets of the cathode compartments of the vats A³ A° and A
and the outlet pipes of these compartments discharge into the reservoir B³.
The reservoir B³ has a number of exit pipes which discharge into the inlets of
the iron anode compartments of the vats A¹ and A. The outlet pipes of these
compartments discharge into the inlets of the iron anode compartments of the
next vats A2 and A. The outlet pipes of these compartments discharge into
the iron anode compartments of the vats A³ and A° and the outlet pipes of these
compartments discharge into the reservoir B.
The reservoir B' has exit pipes which discharge into the inlets of the carbon
anode compartments of the vat A. The outlet pipes of these compartments.
discharge into the inlets of the carbon anode compartments of the vat A³. The
outlet pipes of these compartments discharge into the inlets of the carbon anode
compartments of the 'vat A' and the outlet pipes of these compartments discharge.
into the reservoir B°.
The pumps for raising the solutions from the reservoir B2 to the reservoir B³:
from the reservoir B to the reservoir B as indicated by the arrows on Figure 3
and from the reservoir B" to the leaching vat again, may be of any suitable.
construction and the reservoirs are preferably kept supplied from large storage
anks (not shewn).
The three batches of solution thus circulating consist of portions of the same
tock solution, each undergoing different stages of the operations. That circulating
ast the zinc cathodes must be the solution of the zinc salts from which all iron
as been precipitated by the leaching operation and freed from impurities (if
ecessary) as herein before described. The solution circulating past the iron
nodes is a similar lot of solution which has previously circulated past the zinc
athodes and has thus become more or less depleted of its zinc.
ast the iron anodes until a sufficient quantity of iron has gone into solution as
It is circulated

page_text: ferrous salt. The solution circulating past the carbon anodes has been thus
charged with ferrous salt and it circulates past the carbon anodes until all the
iron it contains has been converted from the ferrous to the ferric state.
It will thus be observed that at each change of the solution the catholyte of
both iron and carbon anode vats becomes the anolyte of the iron anode vats; the
anolyte of the iron-anode vats becomes the anolyte of the carbon vat; the
anolyte of the carbon vats becomes the leaching solution; the leaching solution
after purifying, if necessary, becomes the zinc-bearing solution and the catholyte
of both iron and carbon anode vats, and so the cycle is complete.
The periods at which the changes of the solutions are made will depend upon
various circumstances, mainly upon the amount of the iron which it is found
convenient to impart to the solution-and_the_amount of zinc to remove therefrom
at each cycle.
It will be seen from the chemical reactions hereinafter described that for the
complete and continuous operation of this process two iron anode vats are required
to one carbon anode vat of equal depositing capacity. The process is continuous
and the solution passes through a cycle of operations thus-beginning with a ferric
solution containing more or less zinc and acting on the oxidized ore, the operations
are as follows first: leaching whereby iron is thrown out of solution and zinc
substituted; second: circulation past the cathodes in the zinc electro-depositing
plant where the excess of zinc is taken out; third: circulation past the iron
anodes where ferrous salts are imparted to the solution; fourth circulation past
the carbon anodes where the ferrous salts are oxidized to ferric salts and the
solution thereby regenerated and ready to be again employed for leaching.
Although I have found carbon anodes the most efficient and economical means
for oxidizing the ferrous salt solution to the ferric state I would have it understood
that this may also be effected by known and suitable chemical reagents, such for
instance as chlorine gas as will be well understood.
The use of iron anodes followed by the use of carbon anodes besides affording
an economical means of obtaining iron salts in the solution for leaching the ore
with, prevents the setting free of large amounts of acids in the solution by
electrolysis (also the polarization accompanying the formation of such acids) and
which acids if allowed to remain and come in contact with cathode plates would
render the continuous deposition of the zinc impracticable. The useful purpose of
very materially reducing the energy required to decompose the zinc saits is also
served. The energy represented by the solution of the iron in the iron anode vats
and its higher oxidation in the carbon anode vats approaches very closely to the
total energy required to separate the equivalent amount of zinc at the cathodes.
For the foregoing reasons, the production of zinc by this process is unhampered
by technical irregularities and requires very much less electrical power than by
any electrolysis process hitherto employed and both the first cost and cost of
maintenance of the electrolysis plant are proportionately reduced.
For the soluble iron anodes cast, wrought, or scrap iron or steel may be used.
For the insoluble anodes gas retort carbon, prepared carbon, platinum, ferro-
silicon or any other known and suitable substances may be employed. For the
diaphragms filter-cloth or any of the known porous materials used for electrolysis
may be employed. For the cathode plates almost any metal may be used but I
prefer to employ sheets of zinc which may be melted up in a melting pot with the
deposits obtained or may be stripped and used again and again.
For the above described operations one of several solutions of different, though
analogous, compositions may be employed according to varying circumstances.
No. 1. Zinc chloride mixed with sodium; potassium, magnesium, or ammonium
sulphate.
No. 2. Zinc chloride mixed with sodium, potassium magnesium, or ammonium
chloride.
No. 3. Zinc sulphate mixed with sodium, potassium magnesium, or ammonium
sulnhate

page_text: The ferric salt required in each of the above solutions, in order to effect the
solution of the zinc is generated in the electro-depositing plant as herein before
described, the iron being first imparted by the iron anodes in the ferrous state and
subsequently oxidized to the ferric state.
The strength and the temperature at which the ab
are not material and may vary between very wide lim
generally prefer to employ is the No. 1. solution. Th
to 50 grammes of zinc per litre as zinc chloride
displaced in the electrolysis by the iron salt as ab
to 50 grammes sodium sulphate.
The chemical reactions with this solution are as
of the reactions with the other solutions it will
latter:-
lutions are employed
*The solution which I
fution contains from 10
ich is however partially
mentioned) and from 20
ws, and as they are typical
manecessary to describe the
The lead salts are (at the same time) more or less converted into lead chloride
by a similar reaction and the lead. chloride so produced will re-act with the sodium
sulphate in solution to form insoluble lead sulphate and thus prevent lead from
going into solution, thus
PbCl + Na₂SO₁ = PьSОд + 2 NaCl.
The small quantities of sodium chloride so formed together with the small
quantities of zinc sulphate (basic and neutral) formed in roasting the ore, will
further re-act to re-form sodium sulphate and zinc chloride on boiling the solution
which also throws out the soluble ferric hydrate and silica as hereinbefore
mentioned. If from the proportion of sulphate of zinc in the roasted ore or for
any other reason it is desirable further to lessen the amount of sulphate of zinc it
may be done by the addition of sea-water. In this way any desired proportion of
zinc chloride to zinc sulphate may be arrived at.
When the No. 2. solution is employed, sulphates not being present, any lead
chloride formed will remain unaltered and this salt being slightly soluble it may be
necessary to remove the lead from solution in any well known manner.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. In the treatment of zinc-bearing ores and zinc bearing products the improved
process substantially as herein described.
2. In the treatment of zinc-bearing ores and zinc bearing products the improved
method of leaching by agitating the roasted ores in a finely divided state with a
B

page_text: solution containing an adequate proportion of ferric chloride together with some
sodium, potassium, magnesium, or ammonium sulphate.
3. In the treatment of zinc-bearing ores and zinc bearing products the improved
method of circulating and interchanging the solutions in the double electrolysis
operation substantially as described.
1
1000
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.