IMPROVEMENTS IN TREATING SOLUTIONS OBTAINED FROM BURNT CUPREOUS PYRITES
Year: 1871

page_text: LETTERS PATENT to Frederic Olaudet,. of Nos. 6 and 7, Coleman
-
· Street, in the City of London, for the Invention of "IMPROVEMENTS
IN TREATING SOLUTIONS OBTAINED FROM BURNT CUPREOUS PYRITES."
Sealed the 6th June 1871, and dated the 5th April 1871.
PROVISIONAL SPECIFICATION left by the said Frederic Claudet at the
Office of the Commissioners of Patents, with his Petition, on the
5th April 1871.
I, FREDERIC CLAUDET, of Nos. 6 and 7, Coleman Street, in the City of
5 London, do hereby declare the nature of the said Invention for "IMPROVE-
MENTS IN TREATING SOLUTIONS OBTAINED FROM BURNT CUPREOUS PYRITES," to be.
as follows:-
This Invention has for its object improvements in treating solutions
obtained from burnt cupreous pyrites. In the treatment of Portuguese,.

page_text: Spanish, and other burnt cupreous pyrites by the wet method after
recalcination with salt the waste liquors that remain after precipitation
of the copper contain, as is well known, a large proportion of sodium and
iron salts and some other metallic salts among which are cobaltic
chloride. In the Specification of a former Patent granted to me and 5
dated the 3rd day of November 1866, No. 2858, I proposed employing
these waste solutions for the purpose of making sulphate of sodium and
peroxide of iron. By the process described in this Specification the
oxide of iron is obtained in a crystallino form, and I find that in this
form its mercantile value is less than it is when in the form of rouge. 1
This crystalline form I find to have resulted from the fusion of the salt
which also has the further disadvantage of causing the iron to become
peroxidised partly at the expanse of the sulphuric acid and so the yield
of sulphate of sodium was reduced.
According to my present Invention I proceed as follows:-The 1
solutions are either concentrated in the ordinary "salting down pans"
of alkali works, or in iron pans constructed and heated on the same
principle as those employed in Cheshire for brines, and the salts raked
out as deposited, or they are evaporated to dryness in a reverberatory
furnace. The "yellow salts" or residual mass thus obtained consisting 2
of a mixture of all the alkaline and metallic salts originally in solution
are now charged into a calcining furnace and subjected to a low heat,
taking care to avoid fusion, and to renew the surfaces by repeated and
prolonged stirring. The iron in the salts thus becomes peroxidised, and
the chloride of sodium is more or less completely transformed into 2
sulphate of sodium with the evolution of hydrochloric acid and chlorine.
These gases are made to pass through a tower of the description usually
employed for the condensation of such gases, and being thereby con-
densed serve for the lixiviation of the calcined ores, and for other
purposes. The calcined salts after being withdrawn from the furnace 3
in which the oxidation of the iron has been effected are now treated
with boiling water, by which the soluble salts are dissolved, and a little
lime is added for the purpose of precipitating oxide of cobalt and the
last traces of oxide of iron. The iron oxide and sulphate of calcium
thus separated, together with the oxide of iron left undissolved, on the 3
addition of water to the calcined salts are now separated by filtration,
or otherwise, and the liquors again evaporated to dryness in order to
obtain the soluble salts in a solid form.

page_text: These salts, which mainly consist of a mixture of sulphate of sodium
and chloride of sodium are employed in lieu of common salt for the
manufacture of "salt cake."
The oxide of iron containing a small amount of sulphate of calcium
may be washed up with a little sulphuric acid in order to remove any
traces of caustic lime should such be present, and is dried and employed
as a pigment or otherwise. The oxide of iron thus prepared is not
crystalline, but is in the state of finely divided rouge, and can be
employed as a pigment for the polishing of glass, and for other
purposes.
When in addition to utilising the iron and sodium salts contained in
waste liquors it is desired to extract oxide of cobalt the process is
modified in the following way:-The liquors obtained by treating the
calcined yellow salts with water are separated by filtration or subsidence
from the undissolved rouge, and run into a suitable tank where the
oxide of cobalt, together with traces of nickel, zinc, and manganese, are
precipitated either by milk of lime or caustic alkali, or by an alkaline
carbonate or sulphide. As for the precipitate thus obtained, if not
sufficiently rich in cobalt, it is concentrated by subsequent operations
either by melting with arsenical pyrites into a speiss, or the cobalt is
rendered soluble by roasting, with or without the addition of sulphuric
acid, and separated by the wet way.
As in the former case the alkaline salts are employed in lieu of
common salt in the manufacture of salt cake, but when the above
modification is employed it is not necessary to wash the rouge with
water acidulated with sulphuric acid.