IMPROVEMENTS IN THE TREATMENT OF LEAD AND ARGENTIFEROUS LITHARGE
Year: 1866

page_text: LETTERS PATENT to Clinton Edgcumbe Brooman, of the Firm of
Robertson, Brooman, and Company, of 166, Fleet Street, in the City
of London, Patent Agents, for the Invention of "IMPROVEMENTS IN THE
TREATMENT OF LEAD AND ARGENTIFEROUS LITHARGE."-A communication
from abroad by Frederic Cordurié, of Toulouse, France.
Sealed the 5th March 1867, and dated the 13th December 1866.
PROVISIONAL SPECIFICATION left by the said Clinton Edgcumbe Brooman
at the Office of the Commissioners of Patents, with his Petition, on the
13th December 1866.
I, CLINTON EDGCUMBE BROOMAN, of the Firm of Robertson, Brooman, and
Company; of 166, Fleet Street, in the City of London, Patent Agents, do
hereby declare the nature of the said Invention for "IMPROVEMENTS IN THE
TREATMENT OF LEAD AND ARGENTIFEROUS LITHARGE," to be as follows:-
The object of this Invention is the extraction of silver from lead (chiefly old
lead; that is to say, lead which has been employed. in buildings and otherwise),
and the treatment of litharge.
It is well known that zinc has for silver more affinity than lead. Various
trials: have been made to take advantage of this property in the extraction of

page_text: silver from old lead, but none of them have answered commercially. The
causes which have prevented the employment of zine in the extraction of silver
from lead are, that too much zinc remained in the lead as prepared for the
market, and the scummings composed of lead, silver, and zinc, have not been
treated in an economical manner. Now these difficulties are overcome by the
processes which form the present Invention.
The two characteristic features of these processes are, on the one hand, the
employment of superheated steam to oxidize the zinc and leave the lead and
silver unattached, and, on the other hand, the employment of a forced
passage of oxides of zinc and of lead through a bath of lead which retains all
the silver.
The process for the extraction of silver from lead is divided into two parts;
in the first, I add to the bath of lead in fusion zinc, which after a time causes
the rising of a spongy matter composed in a great part of zinc and silver;
this scummy matter from the lead is separated by a particular treatment,
which constitutes the second part of the process.
First Part. The lead to be treated being well melted, I subject it for a
time to increased heat, after which I add to 100 parts of lead about 2 parts
or more of zinc, taking care to stir it well in the midst of the bath in fusion,
which is then left to itself until the time when the surface begins to coagulate.
This time should not be lost; the melted zinc taking possession of the silver
to produce an alloy less dense and less fusible than the lead rises to the
surface and begins to coagulate, while all the lead preserves its limpidity; it
is now that the scumming must be performed, care being taken to remove the
least possible amount of lead, but leaving none of the alloy in the bath. To
remove the last traces of zinc which remain in the bath of lead, I reheat the
bath, and I lead superheated steam into it. When the superheated steam is
to be introduced I cover the bath, and the steam is conveyed to the bath by
a pipe fitted to the cover and dipping into the bath. The zinc oxidizes under
the action of the oxygen of the decomposed steam, and the oxide of zinc floats
on the surface in the form of powder which I scum off, after which the lead
may be allowed to cool for the market; the hydrogen which is disengaged
may draw off particles of oxide which I then collect in a condenser.
Second Part. The scummings containing lead, silver, and zinc cannot be
completely freed from zinc by a simple distillation in a close vessel; this dis-
tillation would besides have the inconvenience of allowing some of the silver
to be lost. The best means of effecting a complete separation consist in
oxidizing the zinc in the midst of the melted alloy by a current of hot air, or

page_text: preferably by a jet of superheated steam which is admitted at a more or less
considerable pressure by employing a condenser if required. The oxidized zinc,
as well as a certain quantity of lead having an earthy appearance, are easily
separated from the argentiferous lead in fusion by scumming or eliquation.
The lead is sent to be submitted to cupellation, and the oxides are regenerated,
but they are previously made to traverse a bath of lead in which they give off
any silver which they may have drawn off with them as well as traces of oxide
of lead.
The foregoing part of this Invention is thus distinguished, first, by the
employment of superheated steam to oxidize the zinc, while the lead and silver
are not attached; and, secondly, by a forced passage of the oxides in a bath
of lead, which allows of regenerating the zine for use in the next operation.
Another part of this Invention relating to the treatment of litharge is based
on the same principle of the forced passage in a bath of lead. Argentiferous
lead submitted to cupellation produces rich litharge. I remove the silver
which the litharge contains by making it traverse a bath of lead while tho.
litharge is in fusion; the litharge which floats on the top is marketable, and
the lead having become argentiferous is submitted to cupellation.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Clinton Edgcumbe Brooman in the Great Seal Patent Office
on the 13th June 1867.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CLINTON
EDGCUMBE BROOMAN, of the Firm of Robertson, Brooman and Company, of
166, Fleet Street, in the City of London, Patent Agents, send greeting.
.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirteenth day of December, in the year of our
Lord One thousand eight hundred and sixty-six, in the thirtieth year of Her
reigu, did; for Herself, er heirs and successors, give and grant unto me,
the said Clinton Edgcumbe Brooman, Her special licence that I, the said
Clinton Edgcumbe Broonian, my executors, administrators, and assigns, or
such others as I, the said Clinton Edgcumbe Broomau, my executors, admi-
nistrators, and 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, au

page_text: .
Invention for "IMPROVEMENTS IN THE TREATMENT OF LEAD AND ARGENTIFEROUS
LITHARGE," (communicated to me from abroad by Frederic Cordurié, of
Toulouse, France,) upon the condition (amongst others) that I, the said
Clinton Edgcumbe Brooman, 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 manner
the same was to be performed, 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 Clinton Edgcumbe Brooman, do hereby
declare the nature of the said Invention, 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:
The object of this Invention is the extraction of silver from lead (chiefly
old lead, that is to say, lead which has been employed in buildings and other-
wise), and the treatment of litharge.
It is well known that zinc has for silver more affinity than lead. Various
trials have been made to take advantage of this property in the extraction of
silver from old lead, but none of them have answered commercially. The causes
which have prevented the employment of zinc in the extraction of silver from
lead are that too much zinc remained in the lead as prepared for the market,
and the scummings composed of lead, silver, and zinc have not been treated
in an economical manner. Now these difficulties are overcome by the pro-
cesses which form the present Invention.
The two characteristic features of these processes are, on the one hand, the
employment of superheated steam to oxidize the zinc and leave the lead and
silver unattacked, and, on the other hand, the employment of a forced passage
of oxides of zinc and of lead through a bath of lead which retains all the
silver.
The process for the extraction of silver from lead is divided into two parts;
in the first, I add to the bath of lead in fusion zinc, which after a time causes
the rising of a spongy matter composed in a great part of zinc and silver; this
scummy matter from the lead is separated by a particular treatment which
constitutes the second part of the process.
First Part. The lead to be treated being well melted, I subject it for a
time to increased heat, after which I add to 100 parts of lead about 2 parts
or more of zinc, taking care to stir it well in the midst of the bath in fusion,
which is then left to itself until the time when the surface begins to coagulate.

page_text: This time should not be lost; the melted zinc taking possession of the silver
to produce an alloy less dense and less fusible than the lead rises to the
surface and begins to coagulate, while all the lead preserves its limpidity; it
is now that the scumming must be performed, care being taken to remove the
least possible amount of lead, but leaving none of the alloy in the bath. To
remove the last traces of zinc which remain in the bath of lead, I reheat the
bath and I lead superheated steam into it. When the superheated steam is to
be introduced I cover the bath, and the steam is conveyed to the bath by a
pipe fitted to the cover, and dipping into the bath. The zinc oxidizes under
the action of the oxygen of the decomposed steam, and the oxide of zinc floats
on the surface in the form of powder, which I scum off, after which the lead
may be allowed to cool for the market; the hydrogen which is disengaged
may draw off particles of oxide which I then collect in a condenser.
Second Part. The scummings containing lead, silver, and zinc cannot be
completely freed from zinc by a simple distillation in a close vessel; this dis-
tillation would besides have the inconvenience of allowing some of the silver
to be lost. The best means of effecting a complete separation consists in
oxidizing the zinc in the midst of the melted alloy by a current of hot air, or
preferably by a jet of superheated steam which is admitted at a more or less
considerable pressure by employing a condenser if required. The oxidized
zine, as well as a certain quantity of lead having an earthy appearance,
are easily separated from the argentiferous lead in fusion by scumming or
eliquation. The lead is sent to be submitted to cupellation, and the oxides
are regenerated, but they are previously made to traverse a bath of lead in
which they give off any silver which they may have drawn off with them as
well as traces of oxide of lead.
The foregoing part of this Invention is thus distinguished, first, by the
employment of superheated steam to oxidize the zinc while the lead and silver
are not attacked; and, secondly, by a forced passage of the oxides in a bath of
lead which allows of regenerating the zinc for use in the next operation.
Another part of this Invention relating to the treatment of litharge is based
on the same principle of the forced passage in a bath of lead. Argentiferous
lead submited to cupellation produces rich litharge. I remove the silver
which the litharge contains by making it traverse a bath of lead while the
5 litharge is in fusion; the litharge which floats on the top is marketable, and
the lead having become argentiferous is submitted to cupellation.
And having now described the nature of the said Invention, and in what
manner the same is to be performed, I declare that I claim the processes

page_text: herein-before described for the treatment of lead and argentiferous litharge;
and I claim specially the employment of superheated steam to oxidize the
zinc and separate it from the unattacked lead and silver, and the, forced
passage of the oxides of zinc and litharge in fusion in a bath of lead in order
that they may abandon therein the silver which they contain.
In witness whereof, I, the said Clinton Edgcumbe Brooman, have hereunto
set my hand and seal, this Twelfth day of June, One thousand eight.
hundred and sixty-seven.
C. E. BROOMAN. (L.S.)