IMPROVEMENTS IN THE TREATMENT OF CUPREOUS ORES CONTAINING SILVER
Year: 1870

page_text: LETTERS PATENT to Frederic Claudet, of No. 6, Coleman Street, in
the City of London, for the Invention of "IMPROVEMENTS IN THE
TREATMENT OF CUPREOUS ORES CONTAINING SILVER."
COMPLETE SPECIFICATION filed by the said Frederic Claudet at the
Office of the Commissioners of Patents, with his Petition and
Declaration on the 31st January 1870, pursuant to the 9th Section
of the Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, FREDERIC
CLAUDET, of No. 6, Coleman Street, in the City of London, do hereby
declare the nature of the said Invention for "IMPROVEMENTS IN THE
TREATMENT OF CUPREOUS ORES CONTAINING SILVER," 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 :-
This Invention has for its object improvements in the treatment of
AUTOQUE Ores containing silver

page_text: In the extraction of copper from Spanish and Portuguese pyrites and
similar orcs by the ordinary humid process, that is, by roasting the
ground burnt ore with common salt or other chlorides, and subsequently
lixiviating the product, the lye contains copper together with a little
silver and small quantities of some other metals.
Hitherto this silver has been precipitated along with the copper by
means of metallic iron, and their separation has been attempted in various
ways.
According to my Invention I separate or recover the silver previous
to the precipitation of the copper, and I do this by adding to what are
technically called the copper liquors a substance which decomposes the
chloride of silver dissolved in them, and which by combining with the
silver forms iodide of silver. I find that a soluble iodide, such as iodide
of potassium, effects this object by transforming the dissolved chloride of
silver into iodide of silver, and if at the same time the liquors be slightly
diluted a precipitate of subchloride of copper ensues. This precipitate
carrys down with it the insoluble iodide of silver formed. This operation
may be conducted on hot or cold solutions, but I prefer heating them by
means of steam or otherwise. The blowing of steam through the liquors
also facilitates the proper admixture of the iodide solution with them.
From numerous trials it has been found that the proportion of silver
to copper in Portuguese pyrites is about 8 parts in 10,000 parts; an
estimation of the copper present in solution therefore affords in this caso
an easy method of ascertaining the quantity of soluble iodide to be added
so as to avoid an excess. After the addition of the iodide the liquors are,
as before stated, diluted with water until they become slightly turbid,
and are then blown up with steam and afterwards allowed to settle.
The clear liquor is now drawn off to the precipitating tanks, whilst the
sediment contains the silver as iodide of silver, together with subchloride
and oxychloride of copper, some lead, salts and oxides of iron.
I dissolve out the subchloride and oxychloride of copper in the sediment
before referred to by means of very weak hydrochloric acid. After
washing the sediment is now heated with water and metallic zinc added.
The iodide of silver is reduced to the metallic state, whilst soluble iodide
of zinc is formed. This is separated from the deposit by filtration or
otherwise, and the amount of iodine in solution determined. The iodide of
ziuc thus produced is now used over again for precipitating a fresh quantity
of silver from the copper liquors, although in the first instance iodide

page_text: of potassium is the salt I prefer to employ. In this way the iodine is
continuously worked over, and comparatively only a small loss of that
substance has to be provided for.
Finally, the residual product, if rich in silver, can either be melted in
crucibles and cast into ingots or sold to the silver refiners or smelters.
What I claim is the separation substantially as above described of
silver from solutions containing chlorides of silver and copper obtained
in the humid treatment of copper and silver ores by precipitating the
silver in the state of iodide of silver, a substance practically insoluble in
such copper liquors.
In witness whereof, I, the said Frederic Claudet, have hereunto set
my hand and seal, this 31st day of January, in the year of our
Lord One thousand eight hundred and seventy.