IMPROVEMENTS IN EXTRACTING .COPPER FROM ITS ORES BY THE HUMID 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
.COPPER FROM ITS ORES BY THE HUMID 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 EXTRACTING COPPER FROM ITS ORES BY THE HUMID
PROCESS."
IN
This Invention has for its object improvements in extracting copper.from its ores
by the humid process.
1 ..
My system consists in the application to ground or pulverized ores of copper of
bydrochloric acid, either manufactured specially for the purpose, or produced as
waste liquor at the alkali works, or of aqua regia, or of the residuum of the chlorine
works, or of the chlorides of iron, or of manganese, or of ferric salts.
The liquors containing the above substances are placed in direct contact with the
ores, and if these do not contain the necessary oxidating agents, then I add man-
ganese or nitric acid to them in sufficient quantity for the purpose; or I introduce
into the liquors to be used either nitrous vapours or chlorine gas, or else I leave
them exposed sufficiently long to atmospheric influences to produce the necessary
degree of oxidation of the contained salts. This process recommends itself by the possi-
bility of re-employing indefinitely the spent liquors after replacing waste and oxygen.
The copper which enters into solution is precipitated by means of iron or zinc in
a metallic state, or by hyposulphites or sulphuretted hydrogen in the shape of a
sulphide easily reducible in an open furnace.

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 COPPER FROM ITS ORES BY
PROCESS."
THE HUMID
The process consists in the application to ground or pulverized crude ores con-
taining copper alone or in combination with gold and silver of hydrochloric acid,
either manufactured specially for the purpose, or produced as waste liquor at the
alkali works, or of aqua regia, either of which may be used along with peroxide of
manganese, or the residuum of the chlorine works or other oxidizing agents, such as
chlorine gas or hypochlorites or perchlorites, either alone or in combination.
The liquors containing the above substances are placed in contact with crude
ores without any previous roasting or calcination of the same, and if these liquors
do not contain the necessary amount of oxidising agents then I add manganese or
chlorine, or both, or hypochlorites, or perchlorides, or nitric acid, or nitrates to them
in sufficient quantity for the purpose; or I introduce into the liquors to be used
either nitrous vapours or chlorine gas, or some other oxidizing agent, or else I leave
these liquors exposed sufficiently long to atmospheric influences to produce the
necessary degree of re-oxidation of the contained salts.
This process, as above described, has never to my knowledge before been applied
to the extraction of copper or other metals from their crude or unroasted ores, and
recommends itself by the possibility of re-employing the spent liquors after replacing
waste and re-oxidizing them, as above stated.
The copper which enters into solution is precipitated in a metallic state by means
of iron or zinc, or by hyposulphites, or by sulphuretted hydrogen in the shape of a
sulphide easily reducible in an open air furnace, or by electrolysis, all of which
processes are well known, and do not form any part of my claim.
The gold and silver are precipitated on copper, or by means of any of the known
chemical agents used for this purpose.
The following is the manner in which I prefer to operate-I take several samples
of the ore I have to treat, and having pulverized them I expose them to the action
of commercial muriatic acid diluted with its own bulk of water. I apply to the
samples different quantities of acid, and allow each to stand for seven days.. I then
examine the samples, and so ascertain the lowest proportion of acid capable of dis-
solving the copper, for it is important that no more acid than necessary should be
used, for otherwise the iron which is then unnecessarily dissolved would occasion
inconvenience in the subsequent operations..
In working with an ore containing 2 per cent. of copper and 45 per cent. of iron,
about 10 per cent. of it's weight of commercial acid will be required. I add to the
acid bioxide of manganese in the proportion of one part of the oxide to five parts of
the real hydrochloric acid. Where the manganese residuum of chlorine works is
obtainable it may be substituted for the oxide. Before using the acid mixture I
pass chlorine gas through it, and cause it to take up as much as it will absorb.
I also add perchloride or iron until the mixture contains 20 per cent. of the per-
chloride.
I pulverize the crude ore, and place it in tanks together with the acid mixture.
I agitate and apply heat by means of stean blown in beneath a perforated false
bottom with which the tank is provided. After about seven days the copper will
usually be completely dissolved, or if the action should be sluggish it may be
hastened by the addition of a small quantity of nitric acid or nitrate of soda.
The solution is drawn off and the copper is precipitated by means of metallic
iron, as is well understood. Where the ore contains an appreciable quantity of the
precious metals, these also will be found in the solution, and they should be first

page_text: precipitated by means of metallic copper. When the copper has been precipitated
the liquors may be brought back to their original strength by the addition of fresh
acid, and they may be re-used.
As a consequence of the theory by which hydrochloric acid and chlorides act on
crude or raw ores, it is evident that these chemical substances may be employed
with analogous results on calcined or burnt ores, and sometimes in practicing my
Invention it is convenient to mix the crude ores with calcined or burnt ores.
All processes known to me in which hydrochloric acid and some oxidizing agent,
such as nitrate of soda, have been previously employed apply to such ores only as
have been previously freed from sulphur by prior calcination or roasting, and never
to the crude ore as it exists in its natural state, as is the case in my process.
The consequence of my Invention is the possibility of the economical re-utilization
of the spent liquors indefinitely, which is not possible by any of the previously
proposed modes of treating crude ores.
What I claim as new in my process is, the use of hydrochloric acid, or of aqua
regia, simultaneously with peroxide of manganese, or peroxide of iron, or both, or
with the residuum of the chlorine works, or with chlorine gas, or chlorides, or
hypochlorites, or other oxidizing agents, as applied to the extraction of copper and
the precious metals when present from crude or unburnt ores, either alone or mixed
with calcined or burnt ores.
In witness whereof, I, the said Henry Doetsch, have hereunto set my hand
and seal, this Seventeenth day of January, in the year of our Lord One
thousand eight hundred and seventy-nine.
HENRY DOETSCH. (L.S.)