A Process for the Production of Oxide of Zinc and Carbonate of Zinc from Ores or other Materials containing Zinc.
Year: 1898

page_text: A Process for the Production of Oxide of Zinc and Carbonate of
Zinc from Ores or other Materials containing Zinc.
I, GILBERT RIGG, of Tudor Villa, Bryn Road, Swansea, in the County of
Glamorgan, Chemist and Managing Director, do hereby declare the nature of this
invention to be as follows:-
The zinc in the ore or other material must be in the form of oxide or carbonate or
metal in order to be available for this process. Sulphides must therefore be calcined
to oxide. The ore or other zinc-containing material is leached with a solution of
carbonate of ammonia or a solution of carbonate of ammonia and ammonium hydrate
whereby the zinc is dissolved. Now I have discovered that in solutions of carbonate
of ammonia or of carbonate of ammonia and ammonium hydrate for any given
percentage of ammonia there is a certain percentage of carbonic acid at which the
capacity for dissolving zinc possessed by the solution is at a maximum and diminishes
if the amount of carbonic acid present is either increased or diminished. In carrying
my invention into effect I prefer to make use of a solution containing that proportion
of carbonic acid which my experience has shown gives the highest possible zinc-
dissolving capacity to the solution. The ore or other zinc-containing material
calcined if necessary is leached with the solution. The insoluble matters are allowed
to settle out and carbon dioxide is passed into the solution. A mixture of hydrated
oxide of zinc and carbonate of zinc is precipitated. This mixture can be converted
into zinc oxide (ZnO) if required by the application of heat. If it is desired to obtain
a pure and white product and the solution has acquired any contamination through
iron or copper contained in the zinc-containing material the iron must be removed
from solution by mixing hydrated oxide of tin (metastannic acid) with the solution
And the copper
& allowing the precipitate to subside or by other suitable means.
must be removed by placing metallic zine in the solution on which the copper
deposits.
I have found that the zine-dissolving capacity of the solution is very rapidly
reduced by increase of carbonic acid above the amount necessary for the maximum
zinc-dissolving capacity.
In certain solutions an increase of 4 lbs. carbon dioxide (CO2) per gallon will
reduce the zinc-dissolving capacity of the solution from 2.3 lbs. zinc oxide (ZnO)
per gallon to 1.25 lbs. The solution is raised again to its maximum zinc-dissolving
capacity by treating with a suitable amount of lime or caustic alkali or other suitable
means whereby the excess of carbonic acid is removed.
I can also obtain a yield of hydrated oxide and carbonate of zinc from a solution of
carbonate of ammonia cr of carbonate of ammonia & ammonium hydrate containing
zine in solution by reducing the amount of carbonic acid in solution below the

page_text: amount necessary to obtain the maximum zine-dissolving capacity by treatment with
lime or soluble caustic alkali or other suitable means.
1
1000
"
A Process for the Production of Oxide of Zinc and Carbonate of
Zinc from Ores or other Materials containing Zinc.
I, GILBERT RIGG, of Tudor Villa, Bryn Road, Swansea, in the County of Glamorgan,
Chemist and Managing Director, 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 my invention is to produce or separate oxide of zine and carbonate of
zine from ores and other materials containing zine.
I have discovered that when material contains zinc in either the metallic form, or
as oxide, or carbonate, or in two or all of these forins, is leached with a solution of
carbonate of aminonia, or of carbonate of ammonia and ammonium hydrate, there is,
for any given percentage of ammonia in the solution, a certain percentage of carbon
dioxide at which the capacity for dissolving zinc possessed by the solution is at a
maximum.
Any alteration in the amount of carbon dioxide in the solution also causes alteration
in its capacity for dissolving zinc, if the quantity of ammonia remains constant. If
the quantity of carbon dioxide in the solution be increased, the dissolving capacity of
the solution is augmented up to a certain point beyond which any further increase
"causes the dissolving capacity to again decrease.
The mode of practising my invention is as follows:-
When, in the material to be treated, the zinc to be dissolved according to this
invention, is not in either the metallic form, or that of an oxide, or a carbonate, the
material is subjected to a preliminary treatment in order to convert the zinc into one
or some of said forms.
For example, if dealing with sulphide of zinc, the same is converted into oxide of
zine by calcination, as well understood.
The material or mixture of materials containing metallic zinc, or oxide of zinc, or
carbonate of zinc, or two or all of these, is leached with a solution of ammonium
carbonate or ammonium carbonate and aminonium hydrate, in order to dissolve any
contained metallic zinc, oxide of zinc, and carbonate of zinc, or either, and in order to
separate the oxide of zinc and carbonate of zinc, the proportion of carbon dioxide in
the solution is changed by addition or subtraction; or the action of the carbon dioxide
so present is partially counteracted by introduction of suitable material for which it
has an affinity and whereby part of the carbon dioxide is absorbed. By this separating
process I may separate oxide of zinc and carbonate of zinc from a solution obtained
otherwise than by leaching ores or other materials containing zinc provided such
solution be of the same nature as above described.
Having decided on what amount of ammonia is to be used in the solution, it is
obviously advantageous to use for leaching purposes that amount of carbon dioxide
which will impart the greatest possible dissolving capacity to the solution. As will
be evident, this can easily be settled once for all by tests. In the case of two solutions
which I have used containing respectively 1.2 and 1.4 lbs. ammonia (NH3) per
gallon, I find that the following are the dissolving capacities (expressed in lbs. of

page_text: It using solution No. 1, 1 should employ 1.1 10s. carbon dioxide (CO2) for leaching
purposes; if solution No. 2, then 1.3 lbs.
Then I can either increase the amount of carbon dioxide in the solution by blowing
in additional gas, or diminish the amount by adding material (for examples lime or
caustic soda) with which some of the carbon dioxide can combine. In either case the
resulting reduction in the dissolving capacity of the solution is accompanied by pre-.
cipitation of part of the zinc in solution, as oxide and carbonate. The latter method
has the disadvantage that it is difficult to reduce the quantity of the carbon dioxide
present without adding something which will adulterate the product or the solution.
I therefore prefer the former, that is, the precipitation by addition of carbon dioxide.
The extent to which the precipitation is to be carried is determined by various con-
siderations. If the carbon dioxide is added to an extent which will cause some of the
ammonia to be converted into bicarbonate, there is a tendency for this body to crystal-
lize out, especially when the amount of ammonia present is rather large (say as in
solution No. 2). This bicarbonate can however always be recovered by washing the
precipitate. In the case of a 14% ammonia solution (1.4 lb. NH, per gallon) I might
start with about 1.3 lbs. carbon dioxide per gallon for leaching, and increase to about
1.7 during precipitation. This would allow a fair yield of precipitate without any
serious amount of crystallization.
The solution is rendered fit for leaching again by removing the excess of carbon
dioxide by lime or other suitable means.
Although I have stated certain suitable proportions by way of example, it is to
be noted that they are subject to variation as may prove desirable in actual
working.
If it is desired to obtain a pure and white product and the solution has
acquired any contamination through iron or copper contained in the zinc con-
taining material, the iron must be removed from the solution by mixing
hydrated oxide of tin (metastannic acid) with the solution and allowing the
precipitate to subside, or by other suitable means. And the copper must be
removed by placing metallic zinc in the solution on which the copper deposits.
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. For producing or separating oxide of zinc and carbonate of zinc from ores or
other materials containing netallic zinc, or oxide of zinc or carbonate of zinc, or all
or two of these substances, dissolving the metallic zinc, oxide of zinc and carbonate
of zine, or such as may be present, by leaching the material or materials containing
the same with a solution of ammonium carbonate or of ammonium carbonate and

page_text: ammonium hydrate and subsequently separating from the solution oxide of zinc and
carbonate of zinc contained therein by altering the proportion of or partially
counteracting or absorbing the carbon dioxide contained in the said solution.
2. For the production or separation of oxide of zinc and carbonate of zine from
ores or other inaterials containing metallic zine or oxide of zinc or carbonate of zinc
or all or two of these substances, dissolving the metallic zinc, oxide of zinc and
carbonate of zinc, or such as may be present, by leaching the material or materials
containing the same with a solution of ammonium carbonate or of ammonium
carbonate and ammonium hydrate containing carbon dioxide in such proportion to the
percentage of ammonia in the solution as to impart to the latter a maximum zine
dissolving capacity, as herein set forth, and subsequently separating from the solution
oxide of zinc and carbonate of zinc contained therein by altering the amount of
or partially counteracting or absorbing the carbon dioxide contained in the
said solution whilst keeping constant the quantity of ammonia, substantially as
described.
3. In the production or separation of oxide of zinc and carbonate of zinc as referred
to in the preceding claims, rendering the solution from which oxide and carbonate of
zinc have been partially separated fit for re-use by again establishing the proper
proportion of carbon dioxide therein as set forth.
4. The process herein described for separating oxide of zinc and carbonate of zinc
contained in a solution of ammonium carbonate or ammonium carbonate and
ammonium hydrate which consists in altering the proportion of carbon dioxide in the
said solution by addition or subtraction or partial absorption of carbon dioxide, as
set forth.
Dated this 21st day of July 1899.
For the Applicants,
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.