AN IMPROVED METHOD OF SEPARATING SILVER FROM LEAD
Year: 1867

page_text: LETTERS PATENT to William George Blagden, of Hackney Wick, in the
County of Middlesex, for the Invention of "AN IMPROVED METHOD OF
SEPARATING SILVER FROM LEAD."-A communication from abroad by
Francisco Marquez-Millan, of No. 7, Rue Liandier, Marseilles, in the
Empire of France.
Sealed the 9th July 1867, and dated the 14th January 1867.
PROVISIONAL SPECIFICATION left by the said William George Blagden
at the Office of the Commissioners of Patents, with his Petition, on the
14th January 1867.
I, WILLIAM GEORGE BLAGDEN, of Hackney Wick, in the County of Mid-
lesex, do hereby declare the nature of the said Invention for "AN IMPROVED
METHOD OF SEPARATING SILVER FROM LEAD," a communication, to be as
follows:-
The improved mode of separating silver from lead relates to the application
of electricity to the molten lead with which a small quantity of zinc has been
incorporated.
The operations which form the subject of this Invention may be carried on
in a pot similar to those used in the method of separating silver from lead by

page_text: ;
crystallization (usually known as "Pattinson's process"). Before the lead is
conveyed into the pot it may (if requisite) be placed in a reverberatory fur-
nace, and there be submitted to a preliminary refining process, which may be
conducted in the ordinary way; from this reverberatory furnace the lead
may be run or otherwise conveyed into the before-mentioned pot, which has
been previously heated to prevent the lead from cooling or to facilitate its
melting the temperature of the lead is then brought to, say, about 430°
Réaumur in order that the zinc to be subsequently added to it may melt in it;
the molten lead is then skimmed, and the dross thus removed may be treated
in a reverberatory furnace with the next charge of lead which undergoes a
preliminary refining process; a quantity of zinc equal to about to per
cent. of the charge of lead in the pot is now introduced into the molten lead
by means of any suitable instrument, and the whole is then thoroughly and
carefully stirred until the mass is well mixed; an electric current, which
may be generated by a suitable battery in connection with one of "Ruhm-
korff's coils," or otherwise, is then by means of conductors caused to pass
through the molten metal; this current, which produces, among other effects,
in most cases a certain tremor in the mass of metal, is continued for a period
varying from 10 to 30 minutes, according to the quantity and parity of the
lead under treatment and to the proportion of silver it contains. Towards the
close of this operation it is advisable to begin to reduce the fire under the pot
in order to facilitate the solidification and separation of the alloy of zinc and
other metals or impurities which is being formed. After the conductors of
the electric current have been withdrawn from the molten metal it is allowed
to remain at rest and to cool for about a quarter of an hour, and the crust
which in the meantime has formed on the surface of the metal is then
removed. The temperature of the metal is now raised to, say, about 430°
Réaumur, and the operation of introducing from about to per cent. of
zinc, followed by the application of the electric current, and the removal of
the crust, is repeated in the manner already indicated. When the lead under
treatment is very impure, or contains a large proportion of silver, it may be
necessary to repeat this process a third or more times in order to desilverize
the lead sufficiently. The silver which is contained in the various crusts or
skimmings taken from the molten metal after each addition of zinc and
passage of the electric current may be recovered by any of the ordinary
methods. The lead, when sufficiently desilverized, is conveyed to a rever-
beratory furnace which has been previously heated, and there undergoes a
refining or annealing process in order to remove the zinc and other impurities
which it has retained; thus purified the lead may be run into ingots for sale.

page_text: The means employed, as well as the proportions and times indicated in the
use of electricity and zinc in operating upon the lead to separate silver.
therefrom, may be varied.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said William George Blagden in the Great Seal Patent Office on
the 12th July 1867.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
GEORGE BLAGDEN, of Hackney Wick, in the County of Middlesex, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Fourteenth day of January, in the year of our Lord
One thousand eight hundred and sixty-seven, in the thirtieth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said William George Blagden, Her special licence that I, the said William
George Blagden, my executors, administrators, and assigns, or such others as
I, the said William George Bladgen, my executors, administrators, 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, an Invention for "AN
IMPROVED METHOD OF SEPARATING SILVER FROM LEAD," a communication to me
from abroad by Francisco Marquez-Millan, of No. 7, Rue Liandier, Mar-
seilles, in the Empire of France, upon the condition (amongst others) that
I, the said William George Blagden, 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 perfornied, 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 William George Blagden, 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 improved mode of separating silver from lead relates to the application
of electricity to the molten lead with which a small quantity of zinc bas been
incorporated.

page_text: The opérations which form the subject of this Invention may be carried on
in a pot similar to those used in the method of separating silver from lead by
crystallization (usually known as "Pattinson's process "). Before the lead is
conveyed into the pot it may (if requisite) be placed in a reverberatory furnace
and there be submitted to a preliminary refining process, which may be con-
ducted in the ordinary way. The object of this preliminary refining process,
is to remove by oxidation any portions of copper, antimony, arsenic, or other
matters that the lead may contain; but in some cases where the lead contains
no other impurities than a little dross the operation may be dispensed with
altogether. Under ordinary circumstances the average duration of the process
is about 12 hours. From this reverberatory furnace the lead may be run
or otherwise conveyed into the before-mentioned pot, which has been pre-
viously heated to prevent the lead from cooling or to facilitate its melting.
The temperature of the lead is then brought to, say, about 430° Réaumur in
order that the zinc to be subsequently added to it may melt in it. Practically
the temperature may be considered about right when it is impossible to keep
the hand at a distance of 2½ feet from the molten metal; the molten metal is
then skimmed, and the dross thus removed may be treated in a reverberatory
furnace with the next charge of lead, which undergoes a preliminary refining
process; the object of this skimming is to remove all the impurities still
retained by the lead; the dross will be treated again in order to extract the
lead that is mixed with it mechanically; a quantity of zinc equal to about
to per cent. of the charge of lead in the pot is now introduced into the
molten lead by means of any suitable instrument, and the whole is then
thoroughly and carefully stirred until the mass is well mixed. The instru
ment found best adapted for this purpose is a ladle provided with a cover and
a long handle and perforated with a number of small holes; this ladle con-
taining a quantity of zinc is placed in the molten metal, where it is allowed to
remain till all the zinc has melted and passed out through the small holes;
the metal may then be stirred by means of this ladle or other stirrers; if the
mixture of the metals is not complete the zinc will separate in lumps instead
of forming a crust on the surface. An electric current which may be gene-
ated by a suitable battery in connection with one of "Ruhmkorfl's" coils or
otherwise is then by means of conductors caused to pass through the molten
inetal; this current, which produces, among other effects, in most cases a
certain tremor in the mass of metal, is continued for a period varying from
10 to 30 minutes, according to the quantity and purity of the lead under
treatment, and to the proportion of silver it contains. The conductors used
are rods of copper with wooden handles; two, four, six, or eight of these con

page_text: ductors may be suspended in the metal in any convenient manner; the current
should be continued until all the zinc has reached the surface, when it ceases
to have any action on the desilverizing of the lead. Towards the close of this
operation it is advisable to begin to reduce the fire under the pot in order to
facilitate the solidification and separation of the alloy of zinc and other metals
or impurities which is being formed. After the conductors of the electric
current have been withdrawn from the molten metal it is allowed to remain
at rest and to cool for about a quarter of an hour, and the crust which in the
meantime has formed on the surface of the metal is then removed. By
reducing the temperature in this way the alloy of zinc becomes solid and
separates itself more readily from the mass of molten metal. The temperature
found desirable for removing the crust is between 360° and 370° Réaumur,
or when the metal has become solid round the sides of the pot to the extent
of about an inch. In removing the crust from the surface a certain quantity
of lead is always carried away too, but this is easily recovered in the subse-
quent treatment of the alloy; the temperature of the metal is now raised to,
say, about 430° Réaumur, and the operation of introducing from about to
per cent. of zinc, followed by the application of the electric current and the
removal of the crust is repeated in the manner already indicated. When the
the lead under treatment is very impure, or contains a large proportion of
silver, it may be necessary to repeat this process a third or more times in
order to desilverize the lead sufficiently.
It is found desirable from time to time to make an assay of the metal in
the ordinary way with a view to ascertain what quantity of zine, if any, it
may be requisite to add to it, or whether the lead is desilverized to the
required degree, say, at least 50 per cent. The silver which is contained in
the various crusts or skimmings taken from the molten metal after each
addition of zinc and passage of the electric current may be recovered by any
of the ordinary methods. The lead when sufficiently desilverized is conveyed
to a reverberatory furnace which has been previously heated, and there
undergoes a refining or annealing process in order to remove the zinc and
other impurities which it has retained. This process lasts about 3 hours, and
it is desirable to carry it on with a brisk flame. Thus purified the lead may
be run into ingots for sale. The meaus employed as well as the proportions
and times indicated in the use of electricity and zinc in operating upon the
lead to separate silver therefrom may be varied.
Having thus described the Invention as communicated to me, and means
by which the same may be carried into effect, I would have it understood
that I do not confine myself to the precise details herein given, as these

page_text: may be varied without departing from the peculiar character of the Inven-
tion; but what I do claim is, the method of separating silver from lead by the
application of electricity to lead in a molten state containing silver, and with
which zinc has been incorporated, substantially as explained.
In witness whereof, I, the said William George Blagden, have hereunto
set my hand and seal, this Eleventh day of July, in the year of our
Lord One thousand eight hundred and sixty-seven.
W. G. BLAGDEN. (L.S.)