AN IMPROVED PROCESS OF EXTRACTING THE OXIDES AND CARBONATES OF ZINC AND COPPER FROM ORES
Year: 1881

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane, in the
"6
County of Middlesex, Patent Agent, for an Invention of AN IMPROVED
PROCESS OF EXTRACTING THE OXIDES AND CARBONATES OF ZINC AND
COPPER FROM ORES." A communication from abroad by Léon Louis Charles
Krafft and John Edward Schischkar, both of Paris, France.
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark
at the Office of the Commissioners of Patents on the 12th April 1881.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of
Middlesex, Patent Agent. "AN IMPROVED PROCESS OF EXTRACTING THE OXIDES
AND CARBONATES OF ZINC AND COPPER FROM ORES." [A communication from
abroad by Léon Louis Charles Krafft and John Edward Schischkar, both of Paris,
France.]
This Invention has for its object the extraction of the oxides and carbonates of
copper and zinc from poor ores containing them, even when mixed with sulphides
of zinc, lead, copper, mercury, &c.
The process is as follows:-
The ore having been first reduced to powder is treated by a solution of caustic
ammonia (the liquid ammonia of commerce), which dissolves the carbonates and
the oxides of copper and of zinc. It is preferred to employ liquid ammonia of
commerce, diluted with its own weight of water, in quantity equalling generally
four times the weight of the ore, which dissolves all the zinc and the copper which
the carbonated ores of those two minerals contain, and which ores are to be found
in great abundance at the mines, being too poor to pay the cost of transport or ·
shipment.
The operation is always performed in closed vessels, and
either of the following ways:-
may be effected in
1st. By leaving the above named solution for 48 hours in contact with the
powdered ore.
2ndly. By filtering the solution through the powdered ore.

page_text: 3rdly. And preferably by agitating by mechanical means the powdered ore with
the alkaline solution for 4 or 6 hours.
Whichever of the three methods is employed there results on the one hand an
ammoniacal solution of zinc or of copper, and on the other hand a magma of the
gangue which was associated with the metal in the ore.
TREATMENT OF THE AMMONIACAL SOLUTION:
The ammoniacal solution after being allowed to settle is conducted without
coming in contact with the air into an iron vessel, where by the action of direct
heat or by the introduction of a jet of steam or otherwise the temperature is
raised to the boiling point and the ammonia is distilled off; the product of this
distillation passes through the condensers and all the liquid ammonia is entirely
recovered and can be repeatedly employed for the same purpose; or the distilled
ammonia can be conducted into a closed vessel containing ore, mixed with twice
its weight of water in which the ammonia will be condensed. The ore is then
attacked directly and the agitation produced by the condensation is substituted
for the mechanical agitation before referred to, thereby shortening to great
advantage the operation.
By this means the operation is rendered continuous, since the ammoniacal
solution of zinc or copper obtained when treated in the same manner will give
up its ammonia, which when again condensed in the water wetting other ore will
attack the latter, and so on, so that with a given quantity of ammonia one can
without any interruption treat any quantity of ore, and it will only be a question
of the number of closed vessels employed. After all the ammonia has been
distilled off from the ammoniacal solutions there remains in the closed vessels a
magma, composed of carbonates and oxides either of zinc or copper which were
contained in solution. This magma is collected with care, dried in the air, and
afterwards calcined to expel all the carbonic acid it might contain, so as to obtain

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Alexander Melville Clark in the Great Seal Patent Office on the
12th October 1881.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of
Middlesex, Patent Agent. " AN IMPROVED PROCESS OF EXTRACTING THE OXIDES
AND CARBONATES OF ZINC AND COPPER FROM ORES." A communication from
abroad by Léon Louis Charles Krafft and John Edward Schischkar, both of Paris,
France.
This Invention has for its object the extraction of the oxides and carbonates of
copper and zinc from poor ores even when mixed with sulphides of zinc, lead,
copper, mercury, &c.
The process is as follows:-
The ore having been first reduced to powder is treated by a solution of caustic
ammonia (the liquid ammonia of commerce) which dissolves the carbonates and
the oxides of copper and of zinc. The solution of ammonia which it is preferred
to employ is the liquid ammonia of commerce diluted with its own weight of
water. The quantity employed is generally equal to four times the weight of the
ore, whereby all the zine and the copper which the carbonated ores of these two
minerals contain are dissolved. These ores are to be found in great abundance
at the mines, being too poor to pay the cost of transport or shipment.
The operation may be performed in either of the following ways but always in
closed vessels:-1st. By leaving the ammoniacal solution for 48 hours in contact
with the powdered ore; 2ndly, by filtering the solution through the powdered
ore; 3rdly, and preferably, by agitating by mechanical means the powdered ore
with the alkaline solution for 4 or 6 hours.
Whichever of these three methods may be employed the result is on the one
hand an ammoniacal solution of zinc or of copper, and on the other hand a magma
of the gangue which was associated with these metals in the ore.
TREATMENT OF THE AMMONIACAL SOLUTION.
The ammoniacal solution after being allowed to settle is conducted without
coming in contact with the air into an iron vessel, where by the application of
direct heat, or by the introduction of a jet of steam, or by other mode of heating,
the temperature is raised to the boiling point and the ammonia is distilled off
entirely. The product of this distillation passes through the condensing worm
and all the liquid ammonia is entirely recovered and can be repeatedly employed
for the same purpose, or the distilled ammonia can be conducted into a closed
vessel containing ore mixed with twice its weight of water in which the ammonia
will be condensed. The ore is thus attacked directly and the agitation produced
by the condensation is substituted for the mechanical agitation before referred to,
thereby advantageously shortening the operation. In this manner the operation
is rendered continuous since the ammoniacal solution of zinc or copper thus
obtained when treated in the same way will give up its ammonia, which when
again condensed in the water wetting a fresh batch of ore will attack the latter,
and so on, so that with a given quantity of ammonia one can treat any quantity
of ore without interruption, it being only a question of the number of closed
vessels to be employed. After all the ammonia has been distilled off from the
ammoniacal solutions there remains in the closed vessels a magma composed of the
carbonates and oxides, either of zinc or copper which were in solution. This
magma is collected with care, dried in the air, and afterwards calcined to
expel all the carbonic acid it may contain so as to obtain pure oxide of zinc or
of copper.

page_text: TREATMENT OF THE GANGUE.
The minerals left in the gangue after the solution by means of the ammonia of
all the oxides and carbonates of zinc and copper are still slightly wetted with
ammonia, which should not be lost. To this end the residue is treated in the
vessel in which it is contained (as it is the solution of ammonia itself which is to
be treated) by means of a jet of steam or other mode of heating. The ammonia
which disengages is collected and used along with the other, as above mentioned.
The gangue, which might contain blende, galena, cinnabar, or other metallic
compounds not attacked by the process, is purified and enriched by this separation
of the carbonates and oxides of zinc or copper the ore contained. To improve still
more this residue it is only necessary to wash it in order to separate the earthy and
other matters from the metallic part, and thereby produce a rich ore.
Carbonate of ammonia in solution may also be used in place of and in a similar
manner to liquid ammonia with the same result.
The oxide of zinc can be converted into zinc white of the purest and whitest
quality by placing in the ammoniacal solution containing the carbonate of zinc
in closed vessels sheets of metallic zinc to which the foreign metals such as
cadmium, copper, &c., which are soluble in ammoniacal salts adhere.
Having described the nature of the said Invention, and the manner of performing
the same, I declare that what I claim as the Invention to be protected by the
herein before in part recited Letters Patent is,-
The process herein described of extracting the oxides or carbonates of copper
and zinc from ores containing them by the employment of ammonia or of carbonate
of ammonia, substantially as specified.
In witness whereof, I, the said Alexander Melville Clark, have hereunto set
my hand and seal, this Twelfth day of October, in the year of our Lord
One thousand eight hundred and eighty-one.
A. M. CLARK. (L.S.)