IMPROVEMENTS IN EXTRACTING COPPER AND SILVER FROM ORES CON- TAINING THOSE METALS
Year: 1861

page_text: LETTERS PATENT to Gustav Bischof, junior, of Swansea, for the Invention
of "IMPROVEMENTS IN EXTRACTING COPPER AND SILVER FROM ORES CON-
TAINING THOSE METALS."-Partly a communication from abroad, by
Dr. Gustav Bischof, Senior Professor of Chemistry and Technology at
the University of Bonn, Prussia.
Sealed the 11th February 1862, and dated the 3rd September 1861.
PROVISIONAL SPECIFICATION left by the said Gustav Bischof at the
Office of the Commissioners of Patents, with his Petition, on the 3rd
September 1861.
I, GUSTAV BISCHOF, junior, of Swansea, do hereby declare the nature of the
Invention for "IMPROVEMENTS IN EXTRACTING COPPER AND SILVER FROM ORES
CONTAINING THOSE METALS," to be as follows:-
This Invention has for its object improvements in extracting copper and
silver from ores containing those metals. For these purposes, when treating
poor copper ores containing lime or dolomie as gangue, the same is first
calcined in an ordinary lime kiln, the product is then washed to remove the
fiue particles of hydrate of lime and magnesia. The washed calcined ore is
then treated according to one of the processes hereafter described.
If the quality of the ore is such as not to require to be subjected to the
calcining and washing process above mentioned, it may at once be mixed with
iron pyrites, and smelted. The product (coarse metal) is then to be finely
pulverized and calcined at a low red heat in a furnace or muffleso constructed
as to be heated externally, provision being made for the passage away of the
gases and vapours from the furnace or muffle, and for a supply of atmospheric
air to the matters which are being calcined therein. By these means the
Din d3

page_text: sulphuret of copper will for the most part be converted into a sulphate of
copper, which is to be lixiviated in water. The residue, after dissolving out
the copper, is then to be treated with dilute sulphuric acid (concentrated
sulphuric acid diluted with about twenty times its measure of water), by which
the oxide of copper, not previously obtained in solution by the process of
lixiviation, will be obtained in solution; and if there be not much antimony
and arsenic, the silver present will also be obtained in a state of solution.
If the ores contain much antimony and arsenic, the residual product obtained,
as above mentioned, is to be again calcined at a higher temperature, mixing
the product with pulverized bituminous coal and with iron pyrites or coarse
metal sulphate of copper or aluminite, or with sulphuret of zinc. The product
obtained by this calcination is to be lixiviated in the resulting wash waters of
the first lixiviating process above mentioned, by which the remainder of the
silver will be obtained in solution. If the ore does not contain silver, then the
second process of calcination will be unnecessary. In some cases raw copper
ore is mixed with aluminite, and the mixture calcined in a muffle or furnace
such as above described, and in like manner silver ores may be treated with
or without aluminite. The copper and silver thus obtained in solution are
precipitated by ordinary well known means, and to facilitate the precipitation
vertical stirrers or rakes of wood are used, or in place of employing the ordinary
means of precipitation, calcined carbonato of magnesia is used for the purpose
of precipitating the copper from the solution. The copper obtained from the
solution is washed with a dilute solution of sulphate of copper to remove the
metallic iron, afterwards with water, and then with an alkaline solution to
remove the basic sulphate of peroxide of iron; the copper is theu roasted to
remove metallic antimony and arsenic, and then smelted.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by tho said Gustav Bischof in the Great Seal Patent Office on the
3rd March 1862.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GUSTAV
Biscuor, junior, of Swansea, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Third day of September, in the year of our Lord
One thousand eight hundred and sixty-one, in the twenty-fifth year of Her
reign, did, for Herself, Her heirs and successors, givo and grant unto me,
the said Gustav Bischof, Her special licence that I, the said Gustav

page_text: Bischof, my executors, administrators, and assigns, or such others as
I, the said Gustav Bischof, my executors, administrators, or assigns,
should at any time agree with, and no others, from time to time and at
all times thereafter during the term therein expressed, should and lawfully
might make, use, exercise, and vend, within the United Kingdom of Great
Britain and Ireland, the Channel Islands, and Isle of Man, an Invention
for "IMPROVEMENTS IN EXTRACTING COPPER AND SILVER FROM ORES CONTAINING
THOSE METALS," the result partly of communication from abroad, made to me
by Dr. Gustav Bischof, Senior Professor of Chemisty and Technology at the
University of Bonn, Prussia, and partly of Invention and discovery made by
myself, upon the condition (amongst others) that I, the suid Gustav Bischof,
my executors or administrators, by an instrument in writing under my, or their,
or one of their hands and seals, should particularly describe and ascertain the
nature of the said Invention, and in what manuer the same was to be per-
formed, and cause the same to be filed in the Great Seal Patent Office within
six calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said Gustav Bischof, do hereby declare the
nature of the said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement thereof, that is to say :-
This Invention has for its object improvements in extracting copper and
silver from ores containing those metals. For these purposes, when treating
poor copper ores containing lime or dolomie as gangue, the same is first
calcined in an ordinary lime kiln at such a low heat as to prevent the copper
and silver being converted into silicates. The product is then washed to
remove the fine particles of hydrate of lime and magnesia, whilst the particles
of the copper and silver remain unaltered; thus the ores are washed without
any considerable loss. The washed calcined ores are then treated according
to one of the processes hereafter described.
If the quality of the ore is such as not to require to be subjected to the
calcining and washing process above mentioned, it may at once be mixed with
about 5 parts of iron pyrites for each part of copper, and iron pyrites or
corresponding parts of sulphur contained in other sulphurets already in the
ore being allowed for and deducted from the quantity above mentioned.
The quantity of iron pyrites may in most cases be adjusted by mixing ores
which have an excess of iron pyrites with others not containing a sufficient
quantity of them. The ore is then to be fused to obtain coarse metal (regulus),
and this product is afterwards finely pulverized and calcined, during a period

page_text: of about 6 hours, at a low red heat, in a furnace or muflo so constructed as
to be heated oxternally, provision being made for the passage away of the
gases and vapours from the furnace ormuffle,and for a supply of atmospheric
air to the matters which are being calcined therein. The heat to be applied
being a very low one, the body of the furnace may be constructed of plates
of clay or iron. The part of the furnace below the mulle is intended to be
used for the evaporation of the solutions, and for the roasting of the pro-
cipitated copper obtainod,as hereafter described; by these means the sulphuret
(bi-sulphide) of copper will for the most part (about 75 per cent.)be converted
into a sulphate of copper, which is to be lixiviated in water. The residue,
after dissolving out the sulphate of copper, is then to be treated with dilute
sulphuric acid (concentrated sulphuric acid diluted with about twenty times
its measure of water), by which the oxide of copper not previously obtained
in solution by the process of lixiviation with water will be obtained in solution..
The process of lixiviating with water and with dilute sulphuric acid may be
combined, the latter being applied at once. Sulphuric acid is produced by
leading the gases from the muflle or furnace above described into lead
chainbers; the sulphuric acid thus obtained is applied without concentration.
As the sulphuric acid produced is ouly partly consumed for dissolving the
oxide of copper,
the surplus may be sold or used for other technical purposes.
If there be but a small quantity of antimony, arsenic, or chlorides in the ore,
the silver present will also be obtained in a state of solution. If the ores
contain much antimony and arsenic, the residual product obtained, as above
mentioned, is to be again calcined in a furnace or mufHe, such as above
described, at a higher temperature, the product being first mixed with pul-
verized bituminous coal, and afterwards with iron pyrites or coarse metal
sulphate of copper, or with sulphuret of zinc or aluminite (sulphate of
alumina), if the same can be obtained as cheaply as for alum works. The
product obtained by this calcination is to be lixiviated in the resulting wash
waters of the firstlixiviating process above mentioned, by which the remainder
of the silver will be obtainod in solution. In case silver is to be extracted,
chlorides contained in the sulphuric acid to be used for the solution are
removed by adding a solution of sulphate of silver, previously produced, to
the sulphuric acid before its application. Small quantities of chlorides in the
ores are volatilized as chlorides of iron and copper. If the ore does not
contain silver, then the second process of calcination and the removing of
chlorides will be unnecessary. In some cases raw copper ore is mixed with
aluminite (sulphate of alumina), and the mixture calcined in a muille or
furnace,such as above described, and in like manner silver ores, not proviously

page_text: fused, may be treated with or without aluminite. The latter will not be
necessary if the ore contains a sufficient quantity of sulphur. The copper and
silver thus obtained in solution are precipitated by ordinary well known means,
and to facilitate the precipitation, vertical stirrers or rakes of wood are used,
on which, in cases of precipitating the copper with iron, stones are to be fixed,
so as to scrape the bottom of the precipitating vessel, which is formed of iron
plates.
In place of employing iron for the precipitation of copper from the solutions,
calcined carbonate of magnesia (magnesite) may be used, or, instead of
maguesite, dolomite, the lime having been removed by the ordinary means.
When solutions of copper are precipitated with calcined carbonate of mag-
nesia, oxide of copper and sulphate of magnesia (Epsom salts) are the
products; the former has to be reduced, and the latter is sold as a valuable
article; or the same may be treated with charcoal, and decomposed into
magnesia and sulphurous acid, the latter being led into the lead clanıbers, and
the magnesia being used again for the precipitation of the copper. Maguesite,
as is well known, occurs in different places as massy rocks. The copper
obtained from the solution is washed with a dilute solution of sulphate
of copper (the last wash water from the process of lixiviation) to remove
the metallic iron, which sometimes is admixed, if it has been precipitated
with iron; afterwards it is washed with water, and then, according to the
quality of copper required, with an alkaline solution of wood ashes, to remove
traces of basic sulphate (bi-sulphate) of peroxide of iron. The copper is then
roasted to remove metallic antimony and arsenic, and finally melted.
The process of extracting copper, above described, may especially be of use
for ores containing much antimony and arsenic, which are removed so as to
produce a very superior quality of metal. Other advantages are the greater
produce of metal, the absence of any considerable quantity of copper smoke,
and the saving of coal, both the latter advantages reudering the erection of
works in many places feasible where works conducted in the usual manner
would be inadmissible; hence, in many cases, a saving may be effected in the
carriage of the ore.
In witness whereof, I, the said Gustav Bischof, have hereunto set my
hand and seal, this Third day of March, in the year of our Lord One
thousand eight hundred and sixty-two.
GUSTAV BISCHOF. (L.S.