An Improved Process for Desilverizing Argentiferous Lead.
Year: 1891

page_text: Date of Application, 27th May, 1891
Complete Specification Left, 29th Jan., 1892-Accepted, 5th Mar., 1892
PROVISIONAL SPECIFICATION.
An Improved Process for Desilverizing Argentiferous Lead.
I ALEXANDER MELVILLE CLARK, of the firm of A. M. & Wm. Clark, of
53 Chancery Lane, in the County of Middlesex, Fellow of the Institute of Patent
Agents, do hereby declare the nature of this invention (a communication to me
by the Deutsche Gold and Silver Scheide Anstalt, vorm. Roessler, of Frankfort-
on-Main, Germany, through their Agents, Wirth and Co., of Frankfort-on-Main,
aforesaid) to be as follows:-
This invention relates to the desilverizing of lead, and has for its object to
produce a substance from which the lead may be readily and completely isolated.
When lead is desilverized in the ordinary manner by means of zinc, instead of
two well defined layers of zinc-silver alloy and lead being formed, as theoretically
required, lead containing zinc is obtained and a mixture of zinc-silver particles
with lead (so-called zinc scum) from which only half the lead can be removed by
eliquation, the remainder being retained with such tenacity that it can only be
separated by a tedious and expensive method, entailing loss of metal.
The cause of this retention is due to the formation, at the high temperature, of
oxides, which interpose between the particles of lead and zinc-silver and thus
prevent the separation.
We have, however, discovered that an addition, of, say, at most half per cent., of
aluminium to the zinc, very effectually hinders its oxidation and by the employment
of this means skimmings are produced (without extra labor) from which a homo-
geneous zinc-silver alloy, containing all the silver, can be easily and completely
separated, to be then treated electrolytically.
The whole of the zinc contained in the skimmings is recovered, and, whilst
effecting a saving of time, wages, fuel, zinc, and wear and tear of plant, a much
higher yield of silver is produced than by any method hitherto employed.
Dated this 27th day of May 1891.
A. MELVILLE CLARK,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Patent Agents.
A. MELVILLE CLARK,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Patent Agents.
COMPLETE SPECIFICATION.
An Improved Process for Desilverizing Argentiferous Lead.
I, ALEXANDER, MELVILLE CLARK of the firm of A. M. & Wm. Clark of
53 Chancery Lane in the County of Middlesex, Fellow of the Institute of Patent
Agents do hereby declare the nature of this invention (a_communication to me
by the Deutsche Gold and Silver Scheide Anstalt vorm. Roessler of Frankfort-
on-Main, Germany, through their agents Wirth & Co. of Frankfort-on-Main
aforesaid) and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
This invention relates to the desilverization of lead by means of zinc, and has
for its object to enable the lead to be readily separated by eliquation.
Hitherto in desilverizing lead by means of zinc, instead of producing two well
defined layers of lead and zinc-silver alloy in accordance with theory, lead
containing zinc and a mixture of lead with zinc and silver intermingled with oxides
of lead and zinc, so-called zinc-scum has been obtained from which the silver can
only be extracted by complicated, expensive, and wasteful methods owing to the
[Price 8d7

page_text: said oxides tending to prevent the separation of the lead from the zinc-silver alloy.
It has, however, been discovered that the addition of, at the most 5 of one per cent.
of aluminium to the zinc effectually prevents the oxidation thereof. If this
aluminium-zinc alloy be dissolved in the lead, even when the lead is heated to a
strong red heat, a crust is obtained free from oxide and containing all the silver
(instead of the usual scum rich in oxides) and wherefrom a homogeneous zinc-
silver alloy may be readily separated by melting out the lead in the pot or crucible
at about 700° C. This zinc-silver alloy consists essentially of zinc and silver, and
is further treated for the recovery of these two metals in the wet way, or
electrolytically. By this means a much higher yield of lead, silver and zinc is
obtained than hitherto, and a great economy of time, wages, and wear and tear of.
plant is effected.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1st. In the process of desilverizing argentiferous lead, treating the lead with
aluminium-zinc alloy (containing at the most 5 of one per cent. of aluminium) in
lieu of the zinc hitherto employed, substantially as specified.
2nd. In the process for desilverizing argentiferous lead, the production of a
homogeneous alloy consisting essentially of zinc and silver by melting out the lead
from the crust which is free from oxide at a temperature of about 700° C. for the
purpose specified.
Dated this 29th day of January 1892
A. MELVILLE CLARK,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.