IMPROVE- MENTS IN THE TREATMENT OF IMPURE LEAD AND OF THE PRODUCTS OBTAINED THEREFROM.
Year: 1876

page_text: LETTERS PATENT to Clement Roswag, of Paris, in the Republic of France,
Mining Engineer, and Hamilton Geary, of Fairlawn, Old Charlton, in the
County of Kent, Captain, Royal Artillery, for the invention of "IMPROVE-
MENTS IN THE TREATMENT OF IMPURE LEAD AND OF THE PRODUCTS OBTAINED
THEREFROM.'
"
Sealed the 11th May 1877, and dated the 15th November 1876.
PROVISIONAL SPECIFICATION left by the said Clement Roswag and
Hamilton Geary at the Office of the Commissioners of Patents on the 15th
November 1876.
CLEMENT ROSWAG, of Paris, in the Republic of France, Mining Engineer, and
HAMILTON GEARY, of Fairlawn, Old Charlton, in the County of Kent, Captain,
Royal Artillery.
"IMPROVEMENTS IN THE TREATMENT OF IMPURE LEAD AND OF
THE PRODUCTS OBTAINED THEREFROM."
This Invention relates to the purification of impure lead, and to the treatment of
the products obtained therefrom, and consists in the treatment of lead containing
either gold or silver or other foreign metals so as to separate the same there-
from.
The following is a description of the process employed -We act upon pig lead
in a molten condition, containing either one or both of the before-mentioned
precious metals, and either with or without the presence of antimony, arsenic,
The lead to be treated is melted
iron, or zinc, copper, or mixtures of the same.
down in an ordinary cast-iron crystallizing pan, and we then introduce compressed
atmospheric air, either at the ordinary or at an elevated temperature, by means of
a tube or pipe, or tubes or pipes, either of iron, of fire-clay, or of other suitable
material, and by preference of about 2 inches in diameter; this tube or these tubes
are placed nearly at the bottom of the pan (say about from 4 or 5 inches from the
bottom). The tube or pipe or tubes or pipes are supported vertically by preference,
are introduced into the centre of the pan, which tube or pipe or tubes or pipes is
in communication with a compressed air reservoir. The atmospheric air com-
pressed to the desired extent, say to about from 3 to 4 atmospheres, is then
admitted into the molten lead; at the commencement of the operation the injection

page_text: is by preference slow, and subsequently thie admission is in larger quantity. Nearly
the whole of the impurities contained in-the lead are thus oxidized, and are obtained
in the form of a scum.
The introduction of air is arrested, when a sample of the lead assumes a bluish-
violet hue on. cooling, and ceases to be brittle. After this operation has been
performed the auriferous or argentiferous lead may then be subjected to the
ordinary zinc desilverizing process, and the rich dross obtained be submitted to a
process of eliquation with the object of removing the excess of lead contained in the
dross. Having thus effected the separation of the precious metals from the lead
the molten lead is again submitted to the action of atmospheric air in the manner
before mentioned, and the resulting scum removed. The operation is continued
until the lead assumes a bluish-violet appearance on cooling, thus indicating that
a soft lead has been obtained. The purified lead thus obtained may be cast into
pigs or otherwise employed.
The oxides or scums resulting from the first and from the second operation may
be treated by a process known as Roswag's process, via:-The rich dross con-
taining nearly the whole of the precious metals is submitted to the action of
hydrochloric acid in order to dissolve the compounds of zinc, which when dissolved
will be in the state of chloride of zinc, which chloride may be treated by Roswag's
or other process in order to obtain zine or compound of zinc therefrom. Should
any lead be dissolved with the zinc it may be precipitated in a metallic state, and
may be added to the residual lead containing gold or silver, or be otherwise
employed. The residue containing the precious metals being thus freed from zine
and a certain portion of the lead is washed and may then be melted down. When
a sufficient quantity of the rich lead thus resulting is obtained it is to be melted
down, by preference in a cast-iron pan and submitted to the action of compressed
atmospheric air with the object of effecting the oxidation of the whole, or of the
greater proportion of the lead, the litharge thus produced being removed; should
any residual argentiferous lead remain it is to be submitted to a subsequent
operation. The litharge thus obtained is then treated with acetic or with pyro-
ligneous acid. Any silver contained in or mixed with the litharge will remain at
the bottom of the vessel, together with some metallic lead, should any remain
unoxidized. After washing the silver residue it may be melted down and refined.
The solution of acetate of lead resulting may be crystallized or otherwise employed.
After having submitted the lead to the so-called zine desilverizing process, and
having removed the scum or scoria therefrom we effect the separation of the zinc
contained in the lead to the before-mentioned process, vist, the injection of air into
the molten metal, and continue the same until the entire or partial separation of
the zinc is effected. The scum or scums thus resulting may be treated by pre-
ference by what is known as Roswag's process, but the separation of the lead con-
tained therein may be effected by any other process.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Clement Roswag and Hamilton Geary in the Great Seal Patent Office
on the 15th May 1877.
CLEMENT ROSWAG, of Paris, in the Republic of France; Mining Engineer, and
HAMILTON GEARY, of Fairlawn, Old Charlton, in the County of Kent, Captain,
Royal Artillery. "IMPROVEMENTS IN THE TREATMENT OF IMPURE LEAD AND OF
THE PRODUCTS OBTAINED THEREFROM."
The said Invention relates to the purification of impure lead, and to the treat-
ment of the products obtained therefrom, and consists in the treatment of lead
containing either gold or silver or other foreign metals so as to separate the same
.therefrom,

page_text: The following is a description of the process employed-We act upon pig lead
in a molten condition, containing either one or both. of the before-mentioned
precious metals, and either with or without the presence of antimony, arsenic, iron,
or zinc, copper, or alloys of the same. The lead to be treated is melted down in
an ordinary cast-iron crystallizing pan, and we then introduce compressed atmo-
spheric air, either at the ordinary or at an elevated temperature by means of a tubo
or pipe, or tubes or pipes, either of iron, of fire-clay, or of other suitable material;
and by preference of about two inches in diameter; this tube or these tubes are.
placed nearly at the bottom of the pan (say about from four or five inches from the .
bottom). The tube or pipe or tubes or pipes are supported vertically by preference,
are introduced into the centre of the pan, which tube or pipe or tubes or pipes.is.
in communication with a compressed air reservoir or other contrivance. The
atmospheric air is compressed to the desired extent, say to about from three to four
atmospheres, is then admitted into the molten lead; at the commencement of the
operation the injection is by preference slow, and subsequently the admission is in
larger quantity. Nearly the whole of the impurities contained in the lead are thus
oxidized and obtained in the form of a scum or cross.
The introduction of air is arrested when a sample of the lead assumes a bluish-
violet hue on cooling and ceases to be brittle. After this first operation has been
performed the auriferous or argentiferous lead may then be subjected to the ordinary
zine desilverizing process, and the rich dross obtained be submitted to a process of
eliquation with the object of removing the excess of lead contained in the dross.
Having thus effected in this second operation the separation of the precious metals
by means of zinc from the lead the molten lead is again submitted to the action of
atmospheric air in the manner before mentioned, and the resulting scum which
contains the last traces of zinc removed. This third operation is continued until
the lead assumes a bluish-violet appearance on cooling, thus indicating that a soft
lead has been obtained. The purified lead thus obtained may be cast into pigs.or
otherwise employed.
The oxides or scums resulting from the first and from the third operation by
atmospheric air may be treated by a process known as Roswag's or other process.
The rich dross, alloy of silver, zinc, and lead resulting from the second operation
by addition of zinc containing nearly the whole of the precious metals is submitted
to the action of hydrochloric acid in order to dissolve the compounds of zinc, which
when dissolved will be in the state of chloride of zinc, which chloride may be
treated by Roswag's.or other process in order to obtain zinc or compound of zinc
therefrom. Should any lead be dissolved with the zinc it may be precipitated in a
metallic state by means of spelter, and may be added to the residual lead containing
gold or silver. The residue containing the precious metals and a certain portion of
the lead being thus freed from zinc is washed, and is then melted down in a
reverberatory or other furnace. This we call the fourth operation. When a
sufficient quantity of the rich lead thus resulting is obtained it is to be melted
down, by preference in a cast-iron pan and submitted to the action of compressed
atmospheric air with the object of effecting the oxidation of the whole, or of the
greater portion of the lead, the litharge thus produced being removed; should any
residual argentiferous lead remain it is to be submitted to a similar subsequent and
fifth operation. The litharge thus obtained, containing practically the whole of the
precious metal or metals, is then treated with acetic or pyroligneous acid. Any
silver contained in or mixed with the litharge will remain at the bottom of the
vessel together with some metallic lead, should any remain unoxidized. This is the
sixth and principal operation. After washing the silver residue it may be melted
down and refined. The solution of acetate of lead resulting may be crystallized or
otherwise employed.
Having now described and particularly ascertained the nature of our said
Invention and the manner in which the same is or may be used or carried into
effect, we would observe in conclusion that what we consider to be novel and

page_text: original, and therefore claim as the Invention secured to us by the herein-before in
part recited Letters Patent is,―
First. The introduction of blasts of air in the particular manner as before
described into lead when in a molten condition so as to eliminate impuritics there-
from.
.
Secondly. The treatment of the oxide of lead or litharge containing either gold
or silver, or both of these precious metals, obtained as herein-before described, by
ineans of acetic or pyroligneous acid, so as to effect their separation, and obtain a
marketable product, viz., acetate of lead, as herein-before mentioned.
In witness whereof, I, the said Hamilton Geary, on behalf of myself and the
said Clement Roswag, have to this our Specification set my hand and seal,
this Fourteenth day of May, One thousand eight hundred and seventy-
seven.
HAMILTON GEARY. (L.S.)