Improvements in Apparatus for Desilverizing Lead.
Year: 1894

page_text: Date of Application. 14th Feb., 1894
Complete Specification Left, 12th Dec., 1894-Accepted, 9th Feb.,
1895
PROVISIONAL SPECIFICATION.
Improvements in Apparatus for Desilverizing Lead.
I, JOSEPH WILSON SWAN of Lauriston, Bromley in the County of Kent,
Gentleman do hereby declare the nature of my invention to be as follows:-
In desilverizing lead by means of zinc in the manner hitherto practiced molten
zinc is introduced into molten lead and the mixture is stirred and, after being
allowed to remain quiescent for a time, the lighter metal which contains the silver
rises to the surface and is removed for further treatment. Sometimes a further
quantity, or further quantities of zinc is, or are, added to the lead to effect the
removal of any silver not removed by the first operation. As this process is an
intermittent one, it involves a very considerable amount of labour and time, and it
is the object of my invention to save labour and time by providing a desilverizing
process which is practically continuous and automatic.
To obtain this result I avail myself of the effect of the insolubility, beyond a
very small amount, of zinc in lead in the molten state, and of the difference in'
their specific gravity which causes them to separate in layers. The lead to be.
desilverized I cause to pass in a molten state down through a stratum of molten'
zinc above a substratum of molten lead with which substratum the lead which
has traversed the zinc stratum unites, and passes away by an outlet which is so
arranged as to allow of the escape of the lead only, the zinc being retained.
Lead can thus be passed through the zinc until the zinc has become sufficiently
charged with silver to require renewal. The lead passing from the one vessel
may be led into another vessel, or several vessels successively, in which it passes
similarly through a further quantity, or further quantities, of zinc to complete
the removal of silver therefrom, and the vessels may be so arranged that when the
zinc in the first vessel is to be removed the second vessel may be brought into
position for first receiving the lead the vessel which was before the first vessel'
afterwards being recharged with zinc and placed in position as one of the series for
receiving the lead from the preceding vessel or vessels. The vessels are provided'
with any convenient means whereby they can be heated to retain the metals in the
requisite molten condition.
The aforesaid vessels may conveniently consist of melting pots (which may be of
iron) each pot having an opening at the upper part into which the lead to be
desilverized is introduced and an opening at, or near, the lower end, or bottom, by
which the molten lead after traversing the molten zinc, passes into an upward.
tending discharge space, or pipe, the outflow from which is at, or about, the level
at which the column of lead in the discharge space, or pipe, balances the column of
metal in the main melting pot. The process can be carried on with one such pot,,
or with any number of such pots, a number, arranged as aforesaid, being preferred
as it is desirable to avoid the necessity for passing the same lead through the same'
pot repeatedly.
In carrying out the operation the pot or pots, is or are, charged with lead

page_text: sufficient to act as a seal to prevent the passage of zinc to the outflow for the lead.
Zinc is then introduced until the column of metal in the pot forces a portion of
the lead up to the level of the outflow for lead. The lead to be desilverized is
then run in upon the zinc (preferably in a sub-divided condition or stream) in the
pot, or the first pot of a series of pots, and the said lead descends through the zinc
and parts with silver as it descends. It then joins the lead which is beneath the
zinc and an equal quantity of lead passes from the outflow this lead passing thence
to the next pot and so on when a series of pots is used and finally into moulds or to
other receptacle. The inlet and outflow of lead is continued until the zinc in the
first pot has taken up such a quantity of silver as to require renewal when the said
zinc is removed. To enable this to be done the pots are provided with com-
munications and valves which can be opened and closed so as to cut off or open
communication between the pots of a series as desired.
Dated this 14th day of February 1894.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, Agents.
Improvements in Apparatus for Desilverizing Lead.
I, JOSEPH WILSON SWAN, of Lauriston, Bromley in the County of Kent,
Gentleman, 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 :-
In desilverizing lead by means of zinc in the manner hitherto practised molten
zinc is introduced into molten lead and the mixture is stirred, and after being
allowed to remain quiescent for a time, the lighter metal which contains the silver
rises to the surface and is removed for further treatment. Sometimes a further
quantity, or further quantities, of zinc is, or are, added to the lead to effect the
removal of any silver not removed by the first operation. It has also been
proposed to pass the lead to be desilverized, in a molten state, down through a
stratum of molten zinc above a substratum of molten lead, with which substratum
the lead which has traversed the zinc stratum unites, and passes away by an outlet
which is so arranged as to allow of the escape of the lead only, the zinc being
retained. It is the object of my invention to save labour and time by providing a
desilverizing apparatus so arranged that the action is practically continuous and
automatic.
To enable this to be done the pots in any suitable number & containing the zinc
upon a substratum of lead are provided with communications and valves which can
be opened and closed so as to cut-off or open communication between the pots of a
series as desired and run off' the zinc from either of them.
Figures 1 and 2 represent in plan and vertical section respectively a pot suitable
for the purposes of my invention. It is of such a depth as to contain sufficient
molten zinc, which is introduced at top, upon a substratum of molten lead, contained
in the bottom of the pot. a is the opening for the outflow of lead through the
upward tending discharge passage a², and overflow a³, at the level at which the
column of lead, in the passage a2 balances the column of metal in the melting pot,
b, is the outlet for zinc, when it is to be removed for obtaining the silver separated
from the lead.
Figures 3 and 4 are corresponding views in which, in place of making the pot as
deep as in Figures 1 and 2, a circuitous path is made for the lead through the zinc
in the pot by means of the alternately inclined trays c. The other parts which
correspond with those shewn in Figures 1 and 2 are marked with the same letters
of reference.

page_text: Figures 5 and 6 are a sectorial elevation and a plan of an arrangement of pots.
like those shewn in Figures 1 and 2 (although they may be like those shewn in
Figures 3 and 4 if preferred). The parts which correspond with those shewn in
the preceding figures are marked with the same letters of reference. The pots
communicate with each other by means of the passages d each controlled by a
valve as at e. fare the outlets for lead when it leaves the last pot of the series
these outlets being controlled by valves as shewn. b are the outlets for zinc also
controlled by valves as shewn.
The vessels I will call 1, 2 and 3 in the order in which they are presumed to be
in communication for the time being in working. The outlets for zinc from all the
vessels are closed. The outlets for lead from vessels 1 and 2 are closed and the
outlet for lead from the vessel 3 is open. The valves e which control the overflow
passages for lead from vessel 1 to vessel 2, and from vessel 2 to vessel 3, are open,
and the valve e, in the passage between vessels 3 and 1, is closed. The vessels
contain the necessary head of molten zinc as aforesaid and molten lead is
introduced into vessel 1 and passes through the zinc therein then up the passage a
therefrom into the vessel 2 down through the zinc therein then up the passage a²
therefrom into the vessel 3 and down through the zinc therein and up the
passage a³ therefrom and out by the discharged passage and valve at f. The zinc
in vessel 1 becomes first charged sufficiently with silver to be drawn off for
treatment for the recovery of the silver which it has taken up from the lead; this
is done by opening the zinc outlet at b. Fresh zinc is then introduced in its place
and the valves are changed so that the vessel which was No. 2 becomes vessel No. 1
and that which was vessel No. 3 becomes vessel No. 2 the vessel which was No. 1
becoming the last of the series. When the zinc in what is now vessel No. 1 becomes
saturated with silver it is similarly discharged and afterwards when recharged is
made the last of the series and so on by manipulating the valves so as to open and
close the passages as first described." X is a furnace for keeping the metals.
molten, but any other mode of heating can be used.
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 I am
aware that it has been proposed to construct apparatus for desilverizing lead by
the action of zinc with inlets for molten lead and with overflows so arranged that
the lead but not the zinc passes out-I therefore make no general claim for such
construction of apparatus but what I claim is.—
For desilverizing lead, vessels provided with inlets for molten lead, and with
overflows so arranged that the lead, but not the zinc, passes out, and from vessel to
vessel, and through the zinc therein, the said vessels being provided with
communications and valves so arranged as to enable communication between the
vessels to be opened and cut off, and the order of succession of the vessels changed.
substantially as, and for the purposes, herein before described.
Dated this 12th day of December 1894.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, Agents.