IMPROVEMENTS IN EXTRACTING COPPER FROM ITS ORES
Year: 1869

page_text: LETTERS PATENT to James Lewis, of the Firm of James Lewis and
Son, of Fenwick Street, Liverpool, in the County of Lancaster,
Merchants, for the Invention of "IMPROVEMENTS IN EXTRACTING COPPER
FROM ITS ORES."-A communication from abroad by Thomas Sterry
Hunt, of Montreal, and James Douglas, junior, of Quebec, both
in the Dominion of Canada.
Sealed the 26th October 1869, and dated the 13th August 1869.
COMPLETE SPECIFICATION filed by the said James Lewis at the
Office of the Commissioners of Patents, with his Petition and
Declaration, on the 13th August 1869, pursuant to the 9th Section
of the Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, BE IT
KNOWN that I, JAMES LEWIS, of the Firm of James Lewis and
Son, of Fenwick Street, Liverpool, in the County of Lancaster,

page_text: "IMPROVEMENTS IN EXTRACTING COPPER FROM ITS ORES," (communicated to
me from abroad by Thomas Sterry Hunt, of Montreal, and James
Douglas, junior, of Quebec, both in the Dominion of Canada,) and in
what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement thereof, that is to
say :-
For the extraction of copper from its ores by this process it should
be in the state of an oxyd or some compound thereof as oxychlorid or
carbonate. These oxydized forms of copper are decomposed under
proper conditions by protochlorid of iron with the production of
dichlorid of copper soluble in certain saline solutions, and in some cases
a portion of protochlorid together with insoluble peroxyd of iron and
more or less insoluble oxychlorid or basic persalt of iron, which may
be rendered soluble by the action of sulphurous acid. The pulverized
and naturally or artificially oxydized ores are to this end to be digested
with a watery solution of neutral-protochlorid of iron with or without
the addition of an alkaline or earthy chlorid, as common sea salt. The
neutral protochlorid of iron 'may be conveniently prepared by double
decomposition of protosulphate of iron with an equivalent of chlorid
of sodium or chloride of calcium. In preparing the solution (herein-
after designated as the bath) we may proceed as follows:-120
pounds of sea salt (chlorid of sodium) or 112 pounds of dry chlorid
of calcium or its equivalent of hydrated chlorid are to be dissolved
with 280 pounds of protosulphate of iron (green copperas) in 100
imperial gallons of water. In place of the above salts we may
substitute an amount of protochlorid of iron prepared by any other
method and containing fifty-six pounds of metallic iron. To the bath
of 100 gallons prepared in either way 200 pounds of common salt
are then added, when the solution ready for use and will be found
capable of chloridizing about 90 pounds of copper. The power of brine
to dissolve the dichlorid of copper formed 'increases greatly with the
strength and temperature. These proportions are convenient, but in the
case of poor ores a solution of one half the strength may be used with
advantage. In the treatment of copper ores by this process they may
be divided into two classes, non-sulphuretted and sulphuretted ores.
The first class or non-sulpheretted oxydized ores includes the oxyd of

page_text: copper, the carbonates, the oxychlorid, and the red or sub-oxyd. 'To
prepare these for treatment they must all be finely pulverized and the
carbonates may with advantage be gently calcined before or after
grinding in order to expel carbonic acid. The red oxyd if alone or
predominating should also be gently calcined after grinding to convert
it into protoxyd, but if mixed, with a considerable portion of protoxydized
ores, this is not necessary. The pulverized oxydized ores thus prepared
are to be digested with the above bath with frequent agitation. Heat
is not necessary, but a heat of ebullition greatly accelerates the solution
of the oxyds of copper which in practice should not be equal to more
than 60 or 70 pounds of copper for 100 gallons of the above bath. When
the solution is complete and the liquid drawn off, the insoluble residue
should be lixiviated with a small volume. of hot strong brine. The
liquid is then digested with metallic iron, by which the copper is thrown
down as cement copper, two parts by weight of iron yielding about
three parts. of metallic copper.. The bath thus freed from copper
contains a large amount of regenerated protochlorid of iron and can
be used at once to treat a fresh portion of oxydized copper ore. A small
loss of chlorine which separates as oxychlorid has however to be supplica
by adding to the bath from time to time p:otochlorid of iron or the
salts required to produce it. This however need not exceed for cach
repetition one-eighth of the original quantity of iron salt, and by careful
exclusion of the air may be reduced to much less. The strength of the
bath in protochlorid of iron should be determined from time to time by
appropriate tests. In localities where it may be desirable to economize
the protosulphate or protochlorid of iron, a modification of the process
may be adopted, which consists in treating with sulphurous acid the
iron compounds precipitated by the oxyd of copper. To this end
sulphurous acid from the roasting of sulphuretted ores or from any other
source is made to pass over or through the bath after or during the
process of dissolving the oxyd of copper. In the latter case the
protosalts of iron are constantly regenerated and serve to chloridize
fresh portions of oxyd of copper, so that a small amount of protochlorid
of iron with the aid of sufficient common salt and sulphurous acid may
be employed to convert a large quantity of copper into dichlorid, the
excess of which is precipitated and may be dissolved by hot strong.
brine which deposits a large portion of it on cooling, a property which,
may be taken advantage of to use the same brine indefinitely by heating.

page_text: and cooling each time. The solid dichlorid is rapidly reduced by contact
with iron, especially when wet with brine, and yields metallic copper and
protrochlorid of iron, one part of iron giving two parts of copper. To
prevent the partial precipitation of oxychlorid of copper from the
dichlorid solution by the air it is well in all cases to have a small portion
of a protosalt of iron present. A little free sulphurous acid will also
prevent such precipitation, but should be expelled or allowed to escape
from the solution before adding metallic iron. In the case of sulphu-
retted ores of copper the first step in the application of our process has
for its object to convert the metal into an oxyd soluble in the bath
already described. This conversion is effected by thorough calcination
in the air, by which means all copper, iron, and sulphur are oxydized.
I prefer to this end to pulverize the sulphuretted ores and roast them
in a muffle furnace with frequent stirring, a low red heat suffices,
and what is called a "dead roast" is to be avoided, not only because
it involves a waste of time and fuel, but because the high temper-
ature required renders a portion of the oxyd of copper insoluble in
the protochlorid bath. The roasting need only be continued until the
complete oxydation of the sulphuret of copper and its conversion
into a mixture of oxyd with a variable proportion of sulphate of
copper. This product may be treated directly with the bath without
addition as directed for non-sulphuretted ores, but the excess of
sulphates thus, introduced renders the bath impure and much more
metallic iron is required for the subsequent precipitation than when the
whole of the copper is in the form of oxyd. I therefore prefer to
proceed as follows:- I determine in the roasted ore the amount of copper
present as sulphate, which will vary but little for a given ore roasted
under constant conditions, and I add thereto an equivalent of lime,
which gives rise to insoluble sulphate of lime and oxyd of copper. In
practice it is well to leave undecomposed a small amount of sulphate
of copper, which in a subsequent stage of the process will give with
metallic iron the sulphate of iron required to replace the small loss of
chlorine already mentioned. To an ore with eight per cent. of copper.
for instance, which after roasting, holds three per cent. of copper as oxyd
and five per cent as sulphate, I may add lime enough to decompose
four-fifths of the latter at the rate of 280 parts of pure lime for 317
parts of copper or about an equal weight of ordinary non-magnesian
lime, being 4 pounds of finely ground lime for each one hundred

page_text: pounds of the above roasted ore. An equivalent quantity of carbonate
of line or other alkaline or earthly base may be used instead of quick-
lime but with less advantage. The roasted ore and lime may be added
to the bath together, or better the ore first, and the subsequent part of
the process is to be conducted exactly as already described for the ores
of the first class. When protosulphate of iron is used instead of the
protochlorid in preparing the bath or in keeping up its strength as in
the case of ores of the first class, sulphate of soda is formed which may
be in great part crystallized out by extremes of heat or cold. The
formation and accumulation of this sulphate may however be prevented
by the use of an equivalent quantity of chlorid of calcium, as already
indicated. The still large production of sulphate of soda which would
take place if calcined ores of the second class were added directly to the
bath is prevented by the use of lime as already described, and that
portion which must result from the excess of sulphate of copper as
recommended may be decomposed by the addition of small portions of
chlorid of calcium from time to time. By attending to these precautions
the strength of the bath in chlorid of sodium and its solvent power may
be indefinitely maintained.
I wish it to be understood that I do not claim the use of any
particular form of furnace, nor of any special arrangement for calciuing,
lixiviating or precipitating, reserving to myself the choice of the best
forms of apparatus for these purposes, neither do I claim the use of
protosalts of iron otherwise than in solution, nor the use of perchlorid
or other persalts of iron nor yet the use of sulphurous acid save and
except in connection with protosalts of iron as already set forth.
Having now described the nature of the Invention, and in what
manner the same may be performed, I declare that I claim as con-
stituting the present Invention,--
First. The use and application of a solution of neutral protochlorid of
iron or of mixtures containing it for the purpose of converting the
oxyd or sub-oxyd of copper or their compounds into chlorides of
copper.
Second. The use of sulphurous acid for the purpose of decomposing
the oxychlorid of iron formed in the preceding reaction.
Third. The use of a process for the purpose of extracting copper from
its naturally or artificially oxydized ores by the aid of the first or the

page_text: first and second of the above reactions, substantially in the manner
already set forth.
In witness whereof, I, the said James Lewis, have hereunto set
my hand and seal, this Tenth day of August, in the year of our
Lord One thousand eight hundred and sixty-nine.
Witness,
WILLIAM MASSEY,
Book-keeper,
Everton,
Liverpool.
JAMES LEWIS. (L.S.)