Improvements in and relating to the Desilverisation of Lead.
Year: 1896

page_text: COMPLETE SPECIFICATION.
Improvements in and relating to the Desilverisation of Lead.
I, WILLIAM HENRY HOWARD of Pueblo in the County of Pueblo, State of
Colorado, United States of America, Mining Engineer, 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 :-
My invention relates to metallurgy, and its object is to facilitate and cheapen the
process of treating zinc silver crusts in the desilverization of lead.
In what is known as Parkes' process for effecting this result, zinc is stirred into
the molten argentiferous lead, forming an alloy or crust which rises to the surface.
This crust is of mushy consistency and consists of zinc and silver and gold in
granular form, saturated with a large excess of lead only a small portion of which
is combined with the alloy, the greater portion being mechanically mixed therewith.
To liquate the excess of lead in the crust when skimmed off this alloy is sweated
in an iron pot or in a reverberatory or other furnace, additional heat being applied
in each case.
Inasmuch as the melting point of the mechanically mixed pure
lead is lower than that of the alloy, the former melts and drains out of the crust by
gravity.
This method, however, removes only a comparatively small amount of lead.
because much of it seems to be entangled in the crust and will not drain out. The
crust when dry still retains from 75 to 80 per cent. of lead which must be handled
and treated in the subsequent retorting and cupelling processes by which the zinc,
the gold and the silver are extracted from the crust.
My invention relates especially to the treatment of the crust for the purpose of
getting it drier, that is to say, freer from lead, the object being to save time, reduce
the quantity of material to be handled, and bring it into better condition for
treatment in the retorts. I also aim to dispense with the furnace or kettles for
heating the crust, so that the operation can be performed more economically as well
as more quickly.
My improvement consists in subjecting the crust to pressure, whereby the
unalloyed lead is squeezed out, before it has time to cool and harden. Incidentally,
the heat resulting from the pressure may assist in keeping the lead liquid. By
this method I am able to dispense with all additional external heat, and effect a
great saving in time. Moreover, I get rid of a much greater quantity of lead, so
that the resulting alloy is not only considerably reduced in weight and bulk and is
therefore easier to be cupelled, but it runs fifty per cent. higher in silver.
My improvement can be carried out in various ways.
In the accompanying drawing,
Fig. 1, shows in section a desilverizing kettle and a liquating screw-press.
Fig. 2, is a plan view of the same.
Fig. 3, is a modification.
Fig. 4, is a sectional elevation of a press arranged to be kept hot by the lead in
the kettle.
Fig. 5, shows a device for operating such a press by fluid pressure.
The iron kettle A which holds the melted argenti ferons lead B is of the usual
shape and size. Adjacent to this kettle I provide a press, preferably comprising a
cylinder C supported on a suitable foundation D and having perforations c in its
bottom or in the lower portion of its walls, or both, and containing a piston E.

page_text: Any desirable means may be adopted for operating the piston, such as a screw F
working in a nut G formed in or attached to a heavy yoke G¹ spanning the
cylinder. The screw is provided with arms for the like for turning it.
Under the cylinder is placed a trough H inclined toward and terminating over
the kettle A..
The zinc crust b is removed from the surface of the lead by any suitable means,
such as a hand skimmer ladle or the like.
While still hot and mushy, it is put into the cylinder and compressed by the
piston. The squeezed out lead drains through the perforations c and runs back
into the kettle. The operation can be very quickly performed, before the crust
has time to get cool. The pressed and dried cake is then taken out of the cylinder
to be broken up and sent to the retorts. To eject the cake from the cylinder, a
false bottom C may be used, provided with lifting rods c¹ at two or more points.
Or the press may be mounted on a truck I, Figure 1, adapted to be rolled back on
an elevated track, as K, from its position over the stationary trough H, the bottom
of the press being hinged or otherwise removable, so that it can be dropped down,
as shown in dotted lines, to release the cake of crust.
If desired, the cylinder of the press can be placed in the molten lead in the
kettle as shown in Fig. 4. This arrangement utilizes the heat of the lead B to
keep the crust hot and liquate the unalloyed lead therein. The entire press may
be suspended from an overhead carrier L, and by suitable mechanism such as a
cable M, it can be lowered into the kettle.
. When the operation of compressing the alloy is complete the press is hoisted,
run away from the kettle, its bottom removed and the cake forced out of the
cylinder, and dropped on the floor, where it can be broken up ready for the retorts.
When convenient, fluid pressure such as steam or compressed air may be used to
effect the pressing or the hoisting or both. Figure 5 shows one form of apparatus
for utilizing fluid pressure for these purposes. The cylinder N carries a yoke O
from which is hung the cylinder C. In the cylinder N is a piston P whose rod p
is attached to and actuates the piston E of the press. Hose R leads the fluid
pressure to ports above and below the piston P being controlled by a cock r. In
the upper part of the cylinder N is a piston S whose rod s is hung to the overhead
carrier L. A hose R' leads air or steam into the cylinder above the piston S when
the press is to be hoisted. If desired, the fluid pressure can be applied directly to
the surface of the alloy, for instance by admitting it to. the cylinder below the
piston E, or some other tightly fitting cover or lid.
It is evident that many other modifications of the apparatus can be devised,
without departing from the spirit of my invention.
Having thus particularly described and ascertained the nature of my inven
tion aud in what manner the same is to be performed, I declare that what 1
claim is:
1. As an improvement in Parkes' process for desilverizing lead, subjecting the
zine crust to pressure after removing it from the desilverizing kettle, substantially
as described.
2. The process of liquating zinc crusts formed in the desilverization of lead
which consists in subjecting said crusts to pressure without the application of heat,
substantially as described.
3. The process of liquating zinc crusts formed in the desilverization of lead,
which consists in collecting said crusts adjacent to the lead in the desilverizing
kettle, and then subjecting them to pressure to squeeze out the unalloyed lead,
substantially as described.
4. The process of liquating zinc crusts formed in the desilverization of lead,
which consists in collecting said crusts, immersing them in the lead in the desilverizing
kettle, and subjecting them to pressure to squeeze out the unalloyed lead, substantially
as described.
5. The combination with a desilverizing kettle, for the production of zinc crusts

page_text: from lead alloy, of a press, and means for moving said press to and away from said
kettle, substantially as described.
6. In apparatus for the desilverization of lead, the combination with the
desilverizing kettle, of a press comprising a cylinder having a perforated bottom,
and means for lowering said press into said kettle, and raising it therefrom,.
substantially as described.
7. In apparatus for the desilverization of lead, the combination with a desilverizing
kettle, of a press comprising a cylinder having a perforated bottom, means for
raising and lowering said press, and means for conveying it to and from a point
above said kettle, substantially as described.
8. In apparatus for the desilverization of lead, means for applying pressure to
the zine crusts for the purpose of squeezing out the unalloyed lead, substantially as.
described.
Dated the 13th dox of Tul 1905
W. E. HEYS & SON,
Agents for the Applicant.