Improvements in Treating Lead containing Precious Metals.
Year: 1898

page_text: Date of Application, 2nd Aug., 1898-Accepted, 12th Nov., 1898
COMPLETE SPECIFICATION.
Improvements in Treating Lead containing Precious Metals.
I, Dr. WILHELM FEIT, of Langelsheim / Harz, in the German Empire, Manag-
ing Director, do hereby declare the nature of this invention and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement, that is to say:
In the ordinary process for obtaining either lead rich in silver, or pure silver
from poor argentiferous lead, such as raw or hard lead, the oxygen of the air is
utilized for the purpose of converting the lead into oxide of lead, the silver being
left behind.
The object of the present invention is to utilize, for the oxidation of the lead,
oxygen derived from a suitable chemical compound, the product or compound re-
sulting from the reduction of the latter being also obtained in a state in which it
can b. separated and utilized.
Inke manner, the lead may be converted into sulphide of lead by treating
argentiferous lead with a suitable substance containing sulphur, while, at the same
time, the residual compound from the desulphurization of the said substance is
obtained and utilized.
Referring to the oxidation by a suitable compound, I would mention as an
example, that in the operation of producing nitrous salts from nitric salts or
nitrates by means of lead, the latter has heretofore been employed in the pure
state. Thus, besides a nitrous salt, oxide of lead is formed which contains in
admixture as granular particles the excess of lead required for completing the
reaction. This mixture of oxide of lead and lead is then usually transformed into
red lead by oxidation.
Now, according to the present process, I employ argentiferous lead instead of
pure lead, since a further object is to extract the silver from the said argenti-
ferous lead. By causing argentiferous lead to act upon nitrates, it is found that
the reaction takes place in the same manner as with pure lead while, however,
the lead remaining mixed with the oxide of lead contains the whole of the silver
of the argentiferous lead employed. As the excess of lead required for the
reaction amounts practically to about one seventh of the original amount, the
residual lead mixed with the oxide of lead contains seven times the proportion of
silver to that contained in the argentiferous lead.
The separation of this lead rich in silver, from the oxide of lead, may be effected
by washing, or by fusion, but preferably by dissolving the oxide of lead by means
of acids, for example, acetic acid, in which operation acetate of lead is simul-
taneously obtained. If now the lead rich in silver thus obtained be utilized in a
second, third, or further operation, it is evident that, in this manner, a lead will
be obtained which contains 13, 19 and so on times the proportion of silver.
Another example, in which the lead is converted into sulphide, is based upon
the operation of producing cyanides from sulpho-cyanides, argentiferous lead being
however employed instead of pure lead.
On heating sulpho-cyanide of potassium with an excess of argentiferous lead,

page_text: there is obtained, besides cyanide of potassium, a mixture of sulphide of lead and
lead, which latter, also in this case, contains the whole amount of the silver of the
argentiferous lead, the further enrichment of which may be effected in a manner
analogous to that previously mentioned in the first example.
Although in the foregoing examples only argentiferous lead is referred to, yet
it will be readily understood that if the lead should contain gold, the latter would
be obtained in an analogous manner to the silver.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is;
1. The method of treating lead containing precious metals, which consists in
subjecting the same to the action of a suitable chemical compound by which the
greater portion of the lead will combine with oxygen or sulphur, while the pre-
cious metals collect in the excess of lead required for completing the reaction,
substantially as set forth.
2. My improved method or process of treating lead containing precious metals,
substantially as described and for the purposes set forth.
1000
Datou
ERNEST DE PASS,
Chartered Patent Agent,
78, Fleet Street, London, & 5A, Market Street, Nottingham,
Agent for the Applicant.