Improvements in a Process and Apparatus for the Electrolytic Production of Metallic Zinc from Ores of Zinc and Metallic Zinc, and Metallic Copper from Zinc Ores containing Copper, and the Production of Oxygen Gas in the Cases specified.
Year: 1895

page_text: Date of Application, 28th Nov., 1895
Complete Specification Left, 22nd Aug., 1896-Accepted, 10th Oct., 1895
PROVISIONAL SPECIFICATION.
Improvements in a Process and Apparatus for the Electrolytic
Production of Metallic Zinc from Ores of Zinc and Metallic
Zinc, and Metallic Copper from Zinc Ores containing Copper,
and the Production of Oxygen Gas in the Cases specified.
We CHARLES ANTHONY BURGHARDT of 35 Fountain Street in the City of
Manchester in the County of Lancaster Analytical Chemist and GILBERT RIGG
of No. 1 Ellesmere Grove Eccles in the County of Lancaster Analytical Chemist
do hereby declare the nature of this invention to be as follows:-
Our invention relates to the production of metallic zinc from ores of zinc and
metallic zinc & metallic copper from ores of zinc containing copper with the
simultaneous production of oxygen gas in certain cases. The ore whether cupriferous
or otherwise is first roasted to oxide in the usual manner taking special care at the
end of the roasting to so raise the temperature that any sulphate of zinc or sulphate
of copper formed shall be decomposed and converted into the oxides of these
metals. The thoroughly roasted ore is now crushed into powder and placed
in a suitable tank fitted with a mechanical stirrer and a concentrated solution
of either the normal carbonate of ammonium {(NH)2CO₁} or the sesqui-
carbonate of ammonium {(NH),CO, + 2 NH₂HCO3} or the bicarbonate of
ammonium {NH HCO3} or mixtures of these or a solution of ammonia gas in water
poured upon the ore in the tank. Where the solution of ammouia gas in water is
used there is no production of oxygen gas in the later stages of the process. The
liquid in the tank is kept covered with a layer of paraffin oil or other mineral oil
of high flashing point and low viscosity in order to prevent loss of ammonia by
volatilization and the mechanical stirrer set in motion. The oxide of zinc or in the
case of cupriferous ores the oxides of zinc & copper are rapidly dissolved out of
the ore by this treatment. The solution is allowed to settle out all undissolved
material and run out into another tank and again covered with a layer of paraffin
oil or other mineral oil where it is subsequently treated to separate out of it any
dissolved oxides of iron. In the course of our investigations & experiments we
have ascertained that small quantities of the oxides of iron are dissolved by the
above mentioned carbonates of ammonium & solution of ammonia gas in water
and this dissolved iron is highly detrimental in the subsequent electrolytic
deposition of the zinc causing it to fall from the negative pole in a spongy
condition and re-enter into solution whilst what zinc does remain on the negative
pole always contains iron as an impurity. The presence of iron in the deposited
zinc renders it easily soluble in the solution from which it has been electrolytically
deposited. In order to remove the oxides of iron from the solution we add to the
same preferably at a temperature of about 50° Centigrade a certain quantity of
bydrated oxide of tin obtained by any convenient chemical method by preference
by oxidation of metallic tin with nitric acid and subsequent washing and drying of
the product. The hydrated oxide of tin is kept well agitated in the solution and
in a few hours the iron is completely precipitated as oxide. The oxide of tin is
allowed to subside and the clear solution run off. After the hydrated tin oxide
has become saturated with oxide of iron it is placed in a suitable vessel and heated
with sulphuric acid and washed with water which renders it again fit for service
he iron passing into solution as sulphate. In the case of non-cupriferous zinc ores

page_text: the clear solution free from iron. is now ready for electrolysis in the depositing
tanks as described below but if copper was originally present in the ore from
which the solution was made we now proceed to recover it from the solution
purified from iron as above described by placing therein plates of metallic zinc or
preferably plates of metallic zinc & metallic tin in contact acting as a couple.
The copper deposits upon the zinc in hard & bright metallic scales and strips
entirely free from oxide owing to the exclusion of the air by the layer of paraffin
vil or mineral oil. The liquor now free from copper is ready for electrolysis and
is run into the same depositing tanks as the solution from the non-cupriferous zinc
ore both these solutions are from this point treated in the same way. The depositing
tanks are made of wood or other suitable material iron being excluded and the
liquor is covered with a layer of paraffin oil or other mineral oil of high flashing
point and low viscosity and maintained at a temperature of about 50° Centigrade.
The negative poles are made of sheet zinc and the positive poles of tin lead or other
metal not soluble in the liquid. Iron poles cannot be used for the reason given
above. Deposition of zinc at the negative pole and evolution of oxygen gas at the
positive pole commence as soon as the circuit is closed in solutions prepared from
the carbonates of ammonium the zinc being in the form of hard coherent sheets of
bright metallic lustre and easily separated from the negative pole. We find that
for every atom of zinc deposited on the negative pole one atom of oxygen gas is
liberated at the positive pole. We may say here that no hydrogen gas is liberated
throughout the electrolysis. The oxygen gas is collected as it is evolved by any
convenient means and washed with water to remove any traces of ammonia from it.
The sheets of deposited zinc after removal from the negative poles are easily melted
and cast into ingots or otherwise dealt with. The material remaining undissolved
by the carbonates of ammonium or the solution of ammonia gas in water is thoroughly
washed with water under a layer of paraffin oil to recover the contained solution of
ammonium carbonates or ammonia and zinc oxide or zinc & copper oxides. After
depositing the zinc out of the above mentioned solutions the exhausted liquor is run
back into the dissolving tank upon another charge of roasted ore & resaturated
with the oxide of zinc or oxides of zinc and copper as above described and the
above described process repeated.
Dated this 27th day of November 1895.
CHARLES ANTHONY BURGHARDT.
GILBERT RIGG.
COMPLETE SPECIFICATION.
Improvements in a Process and Apparatus for the Electrolytic
Production of Metallic Zinc from Ores of Zinc and Metallic
Zinc, and Metallic Copper from Zinc Ores containing Copper,
and the Production of Oxygen Gas in the Cases specified.
We CHARLES ANTHONY BURGHARDT, of 35 Fountain Street, Manchester, in
the County of Lancaster, Analytical Chemist and Professor of Mineralogy in the
Victoria University, and GILBERT RIGG of No. 1 Ellesmere Grove, Eccles, in
the County of Lancaster, Analytical Chemist, 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 that is to say :-
Our invention relates to the recovery of metallic zipc from ores, of zinc, or
metallic zine and metallic copper from zinc ores containing copper, with
simultaneous production of oxygen gas in the specified instances.
In carrying our invention into effect the ore is first roasted to oxide in the
usual manner, care being taken at the end of the roasting, to, so raise the
.

page_text: temperature that any sulphate of zinc or sulphate of copper formed shall be
decomposed and converted into the oxides of these metals. The thoroughly
roasted ore is now crushed into powder and placed into a suitable tank fitted with a
mechanical stirrer or agitator. We then pour upon the crushed ore in the tank a
concentrated solution of either the normal carbonate of ammonium {(NH4),CO,}
or the sesquicarbonate of ammonium {(NH),CO2 + 2 NH HCO3} or the bicarbonate
of ammonium {(NH,HCO₂)} or mixtures of these or a solution of ammonia gas in
water. We may here mention that where a solution of ammonia gas in water is
used there is no evolution of oxygen gas in the later stages of the process.
Sufficient solution having been poured upon the ore in the tank we next cover the
surface of the liquid with a layer of paraffin oil or other mineral oil of high flashing
point and low viscosity, in order to prevent loss of ammonia by volatilization.
The mechanical stirrer is now set in motion so as to mix the powdered ore
thoroughly with the solution. The oxide of zinc in zinc ores or in the case of zinc
ores containing copper, the oxides of zinc and copper are rapidly dissolved out of
the ore powder by this treatment. The stirrer is then stopped and the solution
allowed to settle, all undissolved mechanically suspended matter falling to the
bottom of the tank, or otherwise the undissolved matter may be separated by
filtration. The solution is then run into another tank and again covered with a
layer of oil as in the first instance. We now treat the solution to remove from it
any dissolved oxides of iron. In the course of our investigations we have ascertained
that small quantities of the oxides of iron are dissolved by the aforesaid carbonate
of ammonium and solution of ammonia gas in water and this dissolved iron is highly
detrimental in the subsequent electrolytic deposition of the zinc, causing it to fall
from the negative pole in a spongy condition and re-enter into solution, while any
zinc which does remain on the negative pole always contains iron as an impurity.
It is therefore essential to remove the oxides of iron from the solution and to do
this we add to the same, preferably at a temperature of about 40 degrees Centigrade,
a proportion of hydrated oxide of tin, obtained by any convenient and well known
chemical method, but by preference by oxidation of metallic tin with nitric acid
and subsequent washing and drying of the product. After adding the hydrated
oxide of tin to the solution, it is kept well agitated by any suitable mechanical
means, and in a few hours the iron in the solution is completely precipitated as
oxide. The oxide of tin is then allowed to subside to the bottom of the tank and
the clear solution is run into a fresh tank. To render the hydrated tin oxide again
fit for service, after it has become saturated with oxide of iron, it is placed in a
suitable vessel and treated with sulphuric acid and washed with water, the iron
passing into solution as sulphate. The iron might however be extracted from the
solution by other means although we at present consider the said hydrated oxide
of tin to be the best agent for the purpose. In the case of zinc ores not containing
copper, the clear solution thus freed from iron is now ready for electrolysis in the
depositing tanks in the manner hereinafter described, but if the ore in the first place
contained copper, we first proceed to recover the copper from the solution by placing
in the tank, plates of metallic zinc or plates of metallic zinc and metallic tin in
contact and acting as a couple. After immersion the copper begins to deposit upon
the zinc in hard, bright metallic scales and strips entirely free from oxide, owing to
the exclusion of air by the layer of mineral oil. The solution is thus freed from its
contained copper and is then run into the same tanks into which the solution is run
when the ore being treated contains no copper, in which latter case the copper
extracting part of the process is omitted. In the zinc depositing tanks the solution
is subjected to electrolysis and is covered as before with a layer of oil and maintained
at a temperature of about 40 to 50 degrees Centigrade. We may here mention
that the tanks used in our improved process after the solution has been freed from
ron should be inade of wood or of other suitable material, iron being excluded
because of its hurtful effect upon the deposition of the zinc. In the electro-
lepositing tanks, the negative poles are made of sheet zinc and the positive poles
of tin, lead or other metal not soluble in the liquor. Iron poles cannot be used for

page_text: the reasons already given. Deposition of zinc at the negative pole and evolution
of oxygen gas at the positive pole commence as soon as the circuit is closed, in
solutions prepared from the carbonates of ammonium, the zinc being deposited in
the form of hard coherent sheets of bright metallic lustre and easily separated from
the negative pole. We have found that for every atom of zinc deposited on the
negative pole one atom of oxygen gas is liberated at the positive pole. No hydrogen
gas is liberated during electrolysis. The oxygen gas is collected as it is evolved
by the means usually employed to trap such gas in the manufacture of oxygen or
by any other convenient means, the gas being washed with water to remove any
traces of ammonia from it. It may be here repeated that no oxygen gas is evolved
in a solution of ammonia gas in water. The sheets of deposited zinc after removal
from the negative poles are easily melted and cast into ingots or otherwise dealt
with. The material remaining undissolved by the carbonate of ammonium solution
or the solution of ammonia gas in water is thoroughly washed with water under a
layer of paraffin or other nineral oil, to recover the contained solution of ammonium
carbonates or ammonia and zinc oxides or zinc and copper oxides. After depositing
the zinc out of the aforesaid solutions, the exhausted liquor is run back into the
first dissolving tank upon another supply of roasted and ground ore, whereupon it
becomes recharged with oxide of zinc and copper as hereinbefore described, the
processes set forth being then repeated.
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.) The improved process for the recovery of metallic zinc from ores of zinc,
by treating the roasted and ground ores with one of the solutions hereinbefore set
forth, freeing the resultant liquor from iron by means of hydrated oxide of tin or
other suitable agent and effecting the electrolytic deposition of the metallic zinc in
the manner and substantially as hereinbefore set forth.
(2.) The improved process for recovering metallic zinc and metallic copper from
zinc ores containing copper, by treating the roasted and ground ores with one of
the described solutions, freeing the resultant liquor from iron by means of hydrated
oxide of tin or other suitable agent, recovering the copper from the solution by
means of immersed zinc or zinc and tin plates and thereafter obtaining the metallic
zine by electrolytic deposition substantially as described.
(3.) The manufacture of oxygen gas effected during the electro-deposition of
ziuc in the course of carrying our improved process into effect, substantially as
herein before described.
(4.) In carrying out the indicated process, preventing the loss of ammonia from
the solution by covering it with a layer of paraffin or other mineral oil as set
forth.
Dated the 21st day of August 1896.
For the Applicants,
E. K. DUTTON & Co.,
5 John Dalton Street, Manchester, Chartered Patent Agents.