Improvements in the Treatment of Ores Containing Zinc.
Year: 1896

page_text: Date of Application, 21st May, 1895
2007
Date of Application, 21st May, 1895
Complete Specification Left, 22nd Feb. 18 7
Accepted, 21st June, 1997
PROVISIONAL SPECIFICATION.
Improvements in the Treatment of Ores Containing Zinc.
I ALEXANDER MELVILLE CLARK, of the Firm of A. M. & Win. Clark, of 53 Chancery
Lane in the County of Middlesex Fellow of the Chartered Institute of Patent Agents
do hereby declare the nature of this invention (a communication to mo by Edgar
Arthur Ashcroft, of 34 Queen Street, Melbourne, Victoria, Australia, Electrical
Engineer) to be as follows:-
The object of my invention is to obtain zinc from ores containing it, in a cheaper
and more convenient manner than heretofore, by the aid of electrolysis.
It is well known that zinc presents great difficulties in electro-deposition inasmuch
as it is liable to form irregular and spongy deposits; acids or salts of the anode metal
are set free at the anode and must be either separated by porous diaphragms from the
liquid around the cathode or the solution must be continuously and rapidly changed in
the electrolysis vats and free acid or metal salts removed.
I have discovered a method whereby from the ore itself (whether zinc blende or a
mixed blende and galena) an aqueous solution of an electrolyte holding a salt of zinc
in solution can be obtained directly, from which zinc can be deposited electrolytically
without any of the above mentioned disadvantages being experienced.
The formation of irregular or spongy deposits during the electro-deposition of zinc
can be prevented by having oxy-salts of the metal present in the solution from which
zinc is being deposited. The solution of oxide of zinc in the aqueous solution of a zinc
salt, e.g. the sulphate or chloride, affords an electrolyte from which zinc can be
electrolytically deposited without the above mentioned disadvantages so long as the
solution still contains oxy-salt of the metal.
To obtain an electrolyte holding oxy-salt in solution directly from the ore I proceed
according to my present discovery as follows:-
The ore is first roasted to convert the sulphate of zinc present as completely as
possible into oxide or sulphate. A portion of the roasted ore is leached with an
aqueous solution of ferric chloride or sulphate, according to the process described in
the amended Specification of Letters Patent No. 13,850 dated July 18th 1894, or is
leached according to the method described in the Specification of Letters Patent
No. 13,534 dated July 13th 1895. By this means an aqueous solution of a zinc
salt is obtained.
Further portions of the roasted ore are then treated as follows:-After being finely
ground they are mixed with finely divided carbon and the mixture is subjected to an
even and correctly gauged temperature of 650 degrees C. (as nearly as possible) for a
time which may be roughly stated at two hours more or less. The zinc sulphate
present undergoes a chemical change, being converted into zinc oxide
follows:-
ZnSO, CZnO + SO, + CO.
as
:
To prepare an electrolyte from which zinc can be deposited without the
disadvantages referred to above, I dissolve in the solution obtained in the leaching
operation referred to above, po:tions of the product resulting from heating as
described above the mixture of finely divided carbon and roasted ore. It is preferable

page_text: The electrolyte obtained by this process may be used for the continuous electro-
deposition of zinc by replenishing the zinc content by dissolving in it from time to
time further portions of the product resulting from heating as described above, the
mixture of finely divided carbon and roasted ore.
In order to obtain the zinc of the ore in the condition of sulphate with a view to
preparing zinc oxide therefrom, if found desirable portions of the ore may be treated
directly with sulphuric acid and roasting dispensed with, or roasting and treatment
with sulphuric acid may be employed conjointly.
In the case where the ore used is a mixed blende and galena, or an impure blende,
it is preferable to employ in the path of the circulating zinc-bearing solution before
the electrolysis vats are reached, apparatus such as settling boxes for removing
the solid residue which remains undissolved after the zinc oxide has gone into
solution.
Dated this 21st day of May 1806
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.
Improvements in the Treatment of Ores Containing Zinc.
I, ALEXANDER MELVILLE CLARK of the Firm of A. M. & Wm. Clark of 53, Chancery
Lane in the County of Middlesex, Fellow of the Chartered Institute of Patent Agents,
do hereby declare the nature of this invention (a communication to me by Edgar
Arthur Ashcroft of 34, Queen Street, Melbourne Victoria, Australia, Electrical
Engineer,) 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 my invention is to obtain zinc from ores containing it, in a cheaper
and more convenient manner than heretofore, by the aid of electrolysis.
It is well known that zinc presents great difficulties in electro-deposition inasmuch
as it is liable to form irregular and spongy deposits; acids or salts of the anode
metal are set free at the anode and must be either separated by porous diaphragms
from the liquid around the cathode or the solution must be continuously and rapidly
changed in the electrolysis vats and free acid or metal salts removed.
I have discovered a method whereby from the ore itself (whether zinc blende or a
mixed blende and galena) an aqueous solution of an electrolyte holding a salt of zinc
in solution can be obtained directly, from which zinc can be deposited electrolytically
without any of the above mentioned disadvantages being experienced.
The formation of irregular or spongy deposits during the electro-deposition of zinc
can be prevented by having oxy-salts of the metal present in the solution from which
zine is being deposited. The solution of oxide of zinc in the aqueous solution of a
zine salt, e.g. the sulphate or chloride, affords an electrolyte from which zinc can be
electrolytically deposited without the above mentioned disadvantages so long as the
solution still contains oxy-salt of the metal.
To obtain an electrolyte holding oxy-salt in solution directly from the ore I proceed
according to my present discovery as follows:-
The ore is first roasted to convert the sulphide of zinc present as completely as
possible into oxide or sulphate. A portion of the roasted ore is leached with an
aqueous solution of ferric chloride or sulphate, according to the process described in
the amended Specification of Letters Patent No. 13,850 dated July 18th 1894, or is
leached according to the method described in the Specification of Letters Patent
No. 13,534 dated July 13th 1895. By this means an aqueous solution of a zinc salt
is obtained.

page_text: Further portions of the roasted ore are then treated as follows:-After being finely
ground they are mixed with finely divided carbon and the mixture is subjected to an
even and correctly gauged temperature of 650 degrees C. (as nearly as possible) for a
time which may be roughly stated at two hours more or less. The zinc sulphate
present undergoes a chemical change, being converted into zinc oxide as
follows:-
ZnSO, CZnO + SO₂ + CO.
To prepare an electrolyte from which zinc can be deposited without the
isadvantages referred to above, I dissolve in the solution obtained in the leaching
operation referred to above, portions of the product resulting from heating, in
the manner described above, the mixture of finely divided carbon and roasted ore. It is
preferable to employ the aqueous solution obtained from the leaching operation hot in
order to increase the amount of the zinc oxide which passes into solution.
The electrolyte obtained by this process may be used for the continuous electro-
deposition of zinc by replenishing the zinc content by dissolving in it from time to
time further portions of the product resulting from heating as described above, the
mixture of finely divided carbon and roasted ore.
In order to obtain the zine of the ore in the condition of sulphate with a view to
preparing zinc oxide therefrom, if found desirable portions of the ore may be treated
directly with sulphuric acid and roasting dispensed with, or roasting and treatment
with sulphuric acid may be employed conjointly.
In the case where the ore used is a mixed blende and galena, or an impure blende,
it is preferable to employ in the path of the circulating zinc-bearing solution before
the electrolysis vats are reached, apparatus such as settling boxes for removing
the solid residue which remains undissolved after the zinc oxide has gone into
solution.
The proportions in which the roasted ore is leached or converted into oxide will
vary according to whether it is desired to use the process as a continuous one for the
electro-deposition of zinc or merely to obtain an electrolyte directly from the ore
containing oxy-salt in solution. If the former be the case, the quantity of roasted ore
leached will be to the quantity converted into oxide relatively very small. If the latter
is the case, the quantity of roasted ore leached will be to the quantity converted into
oxide relatively large.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, I declare that what
I claim is :-
1. The process whereby an electrolyte consisting of a zinc bearing solution in which
an oxy-salt of zinc is present in solution is prepared direct from blende or a mixed
blende and galena substantially as described.
2. The process whereby an electrolyte consisting of a zine bearing solution in which
an oxy-salt of zinc is present in solution is prepared direct from blende or a mixed
blende and galena and by the addition from time to time of zinc oxide prepared in the
manner described, the zinc content of such electrolyte is replenished substantially as
described.
3. The continuous process whereby metallic zinc is obtained from blende or a mixed
blende and galena substantially as described.
Dated this 02nd day of tahm1907
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.