IMPROVEMENTS IN EXTRACTING SILVER FROM LEAD
Year: 1864

page_text: PROVISIONAL SPECIFICATION left by Don Francisco Marques Millan
del Real at the Office of the Commissioners of Patents, with his
Petition, on the 9th May 1864.
I, DON FRANCISCO MARQUES MILLAN DEL REAL, of No. 7, Rue Mautrec,
Bordeaux, in the Empire of France, Engineer, do hereby declare the nature
of the Invention for "IMPROVEMENTS IN EXTRACTING SILVER FROM LEAD," to be
as follows:
This Invention has for its object improvements in extracting silver from
lead. For this purpose lead from which the silver is desired to be extracted
is run from the reverberatory furnace into a heating pan or pans, under which
a strong fire has been previously made in order that no cooling of the lead
may take place, but that its temperature may be raised in a short time; the
surface of the lead is then skimmed, after which I introduce about 1 part by
weight of carbonate of ammonia to every 100,000 parts by weight of lead
contained in the heating pan; the instrument I employ for the purpose of
introducing the carbonate of ammonia into the lead is in the form of a ladle,
having a lid thereto; the entire surface of this instrument is perforated with
small holes, and the lid is provided with a spring catch, by which it is fastened
down.
This instrument, with the carbonate of ammonia therein, is stirred about
in the lead for about five minutes, when it is withdrawn, and a similar
instrument containing about one part by weight of sea salt to about 10,000
parts by weight of lead, is introduced into the lead; this instrument is well

page_text: stirred in the lead for about ten minutes.
If the quantity of silver contained
in the lead is very high, then a proportionally greater quantity of sea salt is
introduced. The surface of the lead is next skimmed, and the products
of this skimming are placed in small heaps, ready to be placed, as hereafter
described, in a close retort, having a condensation chamber or chambers
connected therewith by suitable passages. After this skimming is completed
about 1 per cent. of zinc, is introduced into the remaining lead in an instru-
ment similar to that used for introducing the sea salt and carbonate of
ammonia. The instrument containing the zinc is well stirred in the lead for
about five minutes each time it is introduced, until the desired quantity of
zinc has been added to the lead. The fire is then withdrawn from under the
heating vessel containing the lead, and the door of the furnace is left open in
order that the lead may be cooled as quickly as possible. Directly the surface
of the lead presents a slightly crystalline appearance, this crystallized part is
removed and placed in small heaps, which are then placed without delay in
the retort already referred to, in the following manner :-I first place on the
bottom of the retort a layer of vegetable charcoal broken into small pieces,
upon this the crystallized matter is placed, which is next covered with a layer
of charcoal. The door of the retort is then hermetically closed, and a fierce
fire is made in a furnace under the retort. After maintaining the fire for about
two hours, the zine which was contained in the silver and lead introduced into
the retort will be found in the chambers of condensation in connection with
the retort in the state of oxide of zinc. When the distillation is completed,
which may be readily ascertained by looking through a door into the con-
densation chamber, the retort is opened, and the product of the second
skimming introduced in order to combine it with the silver contained in the
retort, the door is then closed for about ten minutes, after which the rich lead
is drawn off from the retort into a pot, from which it is taken to be refined.
It will be found that all the silver contained in the lead, excepting about 1
to 2 parts of silver to every 10,000 parts of lead, is found reduced to a small
volume with sufficient lead for its cupellation. Directly the crystallized
matters resulting from the third skimming have been introduced into the
retort, the lead remaining in the heating pans or vessels is run off into a
reverberatory furnace, where it is kept under the action of a fierce fire for
about 3 hours, it is then drawn off and cast in suitable moulds.