IMPROVEMENTS IN EXTRACTING METALLIC COPPER FROM ITS ORES BY THE WET PROCESS
Year: 1878

page_text: LETTERS PATENT to Henry Doetsch, of No. 2, Copthall Buildings, in the City
of London, Merchant, for the Invention of "IMPROVEMENTS IN EXTRACTING
METALLIC COPPER FROM ITS ORES BY THE WET PROCESS."
}
Sealed the 1st October 1878, and dated the 19th July 1878.
PROVISIONAL SPECIFICATION left by the said Henry Doetsch at the Office
of the Commissioners of Patents on the 19th July 1878.
HENRY DOETSCH, of No. 2, Copthall Buildings, in the City of London, Merchant.
"IMPROVEMENTS IN EXTRACTING METALLIC COPPER FROM ITS ORES BY THE WET
PROCESS."
My process for extracting copper from its natural sulphides consists in the
calcining the pyrites in a special furnace, which may have the form of a covered
limekiln, or be similar to the sulphate of soda furnaces, or on the type of a
reverberatory furnace, the only condition being that this furnace be placed in com-
munication with a chamber for receiving the sulphur volatilized; and a special
condenser for the sulphurous vapours simultaneously produced.
The heat is obtained by the combustion of a portion of the pyrites, or by any
other kind of fuel, and serves to extract sulphur and sulphurous acid from the
remaining portion of these pyrites.
"
The sulphurous acid collected in the condenser, which latter may be of any shape
or form, is employed to dissolve the copper out of its ores, either crude or calcined
by direct contact, and also for the production of hyposulphite of soda, which is used
in lieu of iron for precipitating the copper in the shape of a sulphide, easily
reducible into metallic copper by fusion in contact with the air.

page_text: -
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Henry Doetsch in the Great Seal Patent Office on the 18th January
1879.
HENRY DOETSCH, of No. 2, Copthall Buildings, in the City of London, Merchant.
"IMPROVEMENTS IN EXTRACTING METALLIC COPPER FROM ITS ORES BY THE WET
PROCESS."
My process for extracting copper from its natural sulphides consists in calcining
or burning of pyrites in a furnace, which may have the form of a covered lime-
kiln, or be similar to the sulphate of soda furnaces, or be on the type of a rever-
beratory furnace, the only condition being that this furnace be placed in communi-
cation with a chamber for receiving the sulphur volatilized, and a condenser for the
sulphurous vapours simultaneously produced..
The heat is obtained by the combustion of a portion of the pyrites, or by any
other kind of fuel, and serves to extract sulphur and sulphurous acid from the
remaining portion of the pyrites in the furnace.
The sulphurous acid collected in the condenser, which latter may be of any shape
or form, is employed hot or cold, either alone or in conjunction with chloride of
sodium, or of manganese, or other chlorides, either separately or combined, without
being transformed into sulphuric acid, to dissolve the copper out of crude or
unroasted ores by direct contact, and it may also be used for the production of
hyposulphite of soda, which may be employed in lieu of iron for precipitating the
copper in the shape of a sulphide, easily reducible into metallic copper by fusion in
contact with the air.
This process comprises two distinct operations, the one of which relating to the
extraction of the sulphur and sulphurous acid is not new, while the second, com-
prising the use of sulphurous acid, either alone or in connection with oxidizing
agents for the extraction of copper from crude, or uncalcined, or unburnt ores, is
new, and has never yet to the best of my knowledge been proposed.
It is well known that the copper may be precipitated in a metallic state from its
solutions by means of metallic iron or zinc, and in the form of a sulphide by means
of hyposulphite of soda or of sulphuretted hydrogen, or it may be thrown down by
electrolysis, either of which I propose employing, but to neither of these do I make
any claim for novelty.
The following is the manner in which I prefer to operate:-I produce the
sulphurous acid which I require by burning pyrites in a kiln like a limekiln, but
domed over at the top. The combustion is conducted with as small an admission
of air as possible, and some of the sulphur contained in the pyrites, usually about
25 per cent., is sublimed. I conduct the vapours by a flue at once into a chamber
like a sulphuric acid chamber, and of like dimensions, proportionally to the quantity
of pyrites burnt, but it need not be of lead, wood will answer the purpose. I
introduce into the chamber also water, in the form of steam, vapour, or spray, in
such quantity that at the bottom of the chamber there is deposited a solution of the
acid vapours. The sublimed sulphur is also deposited in the fore part of the
chamber, and is removed from time to time; it forms a valuable product, which
may be sent to market either in its crude or in a refined form.
But a small proportion of the ore will require to be burnt to produce sulphurous
acid, the remainder is treated in its crude, uncalcined, or unburnt state. I regulate
the quantity of sulphurous acid employed according to the copper per-centage of the
ore, using about 25 per cent. more than the quantity with which the copper can
combine. With a 2 per cent. ore the quantity will generally be about one-fifth of the
weight of the ore of the weak chamber acid...I.prefer to mix with the acid peroxide
of manganese and common salt, each in the proportion of half a part to one part of
real acid in the solution.

page_text: I put the ore, previously pulverized, together with the acid mixture, into tanks,
which may be built of stone, cemented and coated with asphaltum, and I agitate
and heat the whole by blowing in steam by a steam pipe beneath a false bottom,
with which the tank is provided. In about seven days time the acid will have
dissolved practically the whole of the copper, leaving the iron and sulphur in the
ore almost untouched.
The solution is run off in a separate vessel; the copper is precipitated, by pre-
ference, by means of metallic iron, as is well understood, and where the ore contains
an appreciable quantity of silver, as is frequently the case, this may be precipitated
with metallic copper.
I claim, as new, the process above described for extracting copper from its natural
ores by means of sulphurous acid, either alone or in connection with other agents,
as herein set forth..
In witness whereof, I, the said Henry Doetsch, have hereunto set my hand
and seal, the Seventeenth day of January, in the year of our Lord One
thousand eight hundred and seventy-nine.
HENRY DOETSCH. (L.S.)