An Improved Method of Smelting Complex Silver Oreș.
Year: 1891

page_text: COMPLETE SPECIFICATION.
An Improved Method of Smelting Complex Silver Oreș.
I, CHRISTOPHER JAMES, of Ida Villa, Swansea, in the County of Glamorgan,
Metallurgist, 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:-
Silver ores containing more or less gold are almost invariably associated with
arsenic, antimony, sulphur, and also combined with copper in variable percentages,
also a large portion of the silver ores of commerce are largely associated with zinc
blende, these latter ores are most difficult to treat by the ordinary method.
When silver ores do not contain sufficient lead, they are technically called "dry,"
in smelting such ores they are therefore mixed with lead in the form of litharge, or
sulphates, to bring up the percentage of lead in the mixture to about 25 per cent.
of the charge. This mixture of lead and silver ores is now, as a practice, charged
in a cupola furnace with varying proportions of copper-works-slag as a flux, and
smelted, the resulting product consists of metallic lead, copper, matte and slag, the
lead being the carrier of the silver and gold, is found to be very rich, so is also
the copper matte, the slag being comparatively free of silver.
When rich ores are smelted in a blast furnace, as is the practice, large losses are
made, the blast carrying fine particles into the flue, and finally into the air.
Also when silver ores, rich in zinc, are smelted in a blast furnace (which is
essentially a reducing furnace) the zinc is reduced at the smelting zone to metallic
zinc, this again combines with the oxygen of the blast and sulphur of the charge,
and forms zinciferous accretions, which grow on the sides of the furnace so as to
impede smelting to a large extent; and should the per centage of zinc be 25 per cent.
of the charge, which is often the case, the operation becomes tedious and expensive.
Owing to the small amount of this class of ore that can be smelted, silver ore
containing a large per centage of zinc cannot be successfully treated in a blast
furnace, as is at present the practice. Again the necessarily high temperature
required to smelt these complex silver ores in a blast cupola furnace is attended
with a large loss of lead, and a corresponding loss of silver.
In my new process I substitute for the cupola furnace above described (with a
reducing action in the upper part of that furnace always preventing the free escape
of the oxidised zinc) a reverberatory furnace, in which I maintain an oxidising
atmosphere, and from which fumes of zinc, antimony, chlorine, etc., readily escape
when volatilized.
For treatment I propose to classify my ores roughly into two classes as
follows
1. Sulphides.
2. Haloids.
In class one I include pure sulphides, as silver glance, argentiferous blende, and
argentiferous galena, and all those complex arsenical and antimonial silver ores
consisting of sulphide of silver (Ag,S), sulphide of antimony (Sh₂S,) and
sulphide of arsenic (As,S,) combined together, as for instance in the minerals
pyrargyrite (ruby silver ore) proustite, and all the various fahl-ores.
In class two I include all those silver ores in which silver exists in combination
with either or several of the halogins, ás chlorides, bromides, and iodides.
In the treatment of ores in the first class, the ores are crushed fine and intimately
mixed with litharge ;-I have found good results when the weight of litharge has
been such as to oxidise entirely the sulphur present in the ore; thus 5°, sulphur
in the ore requires 14 cwts. litharge to the ton of ore; this mixture is charged into

page_text: a reverberatory furnace and melted, when the sulphur and oxygen re-act upon each
other, metallic lead being reduced, which sinks to the bottom, carrying with it
nearly all the silver in the ore, the sulphur escapes as sulphur dioxide, and the
other basés present may be volatilized in the metallic form (in which case they are
immediately oxidised by the air) or directly given off as, oxides. The resulting
slag is now skimmed off, the furnace is again successively charged and skimmed,
until sufficient lead accumulates, when it is drawn off. If desirable however, I may
commence smelting the mixtures on a bath of lead. The process for two of the
ores in this class when available to be treated together wiz.-argentiferous blende,
and argentiferous galena, may be varied by calcining the former and intimately
mixing the calcined product with the argentiferous galena in the proportion of
16 parts pure blende (calcined) to 24 parts pure galena, when exactly the same
re-action takes place, in this way the sulphur is supplied from the galena and
the oxygen from the calcined ore.
When the ore is argentiferous containing blende, by my process the blende is
converted into zinc oxide, which becomes my oxidising agent in the smelting and
thus of real use, whereas in the usual empola treatment the zinc is a serious draw-
back as it renders the charge very infusible, moreover in the calcination which I
adopt there is little or no loss of silver.
The ores of the second class are mixed with litharge (or oxidised lead ores such
as carbonates) and galenas in the proportion of two of litharge to one of galena as
may be necessary, and dealt with in the furnace in the same manner as the ores of
the first class, the same re-action taking place, lead being reduced and alloying
with the silver breaks up the halogen compounds, the chlorine, bromine, or iodine
is eliminated, and owing to the atmosphere of sulphur gas existing in the furnace,
no loss of silver can take place, which would otherwise be so, as the halogen
compounds of silver are extremely volatile without change, sulphur however by
virtue of its superior affinity for silver entirely obviates this loss, and retains the
silver in the furnace.
I may use any oxidised compound of lead in place of litharge, such as sulphate
of lead (roasted galena).
In each of the above cases, the re-actions are identical and depend upon the
mutual re-action of a sulphide and oxide or other oxidised compound, resulting in
the formation of argentiferous lead. This may be best illustrated by the typical
formula expressing the re-action when sulphide of lead (galena) and oxide of lead
(litharge) are melted together with the production of metallic lead and sulphurous
anhydride viz. :—
PbS2 Pbo = 3 Pb + SO,
precisely similar re-actions occur when sulphides of silver are present with the
sulphides of lead.
processes.
the argentiferous lead is extracted by either of the well known
In this process the volatilized zinc and lead vapours may be collected in suitable
flues and condensing chambers so that loss may be reduced to a minimum.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what 1
claim is :-
1st. A process for the smelting of complex silver ores in reverberatory instead
of cupola furnaces, in which an artificial mixture of oxides and sulphides of the
silver-carrying ore to be treated, and lead, is made, so that a metallic reduction of
the lead, alloying with it the silver is effected, by the re-action of the sulphur and
oxygen upon one another, whilst by the oxidising nature of the atmosphere of a
reverberatory furnace, and the absence of an over-burden and reducing zone, as in
a cupola furnace, the volatilization and escape of the zinc, if present, is ensured
for prompt removal from the furnace, and after collection if desired.
processes.
In this process the volatilized zinc and lead vapours may be collected in suitable
flues and condensing chambers so that loss may be reduced to a minimum.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what 1
claim is :-
1st. A process for the smelting of complex silver ores in reverberatory instead
of cupola furnaces, in which an artificial mixture of oxides and sulphides of the
silver-carrying ore to be treated, and lead, is made, so that a metallic reduction of
the lead, alloying with it the silver is effected, by the re-action of the sulphur and
oxygen upon one another, whilst by the oxidising nature of the atmosphere of a
reverberatory furnace, and the absence of an over-burden and reducing zone, as in
a cupola furnace, the volatilization and escape of the zinc, if present, is ensured
for prompt removal from the furnace, and after collection if desired.

page_text: nd. As a specific process (for the treatment of sulphide silver carrying ore).
a.) The addition to the said ores of litharge in an oxidising reverberatory
furnace, causing the metallic reduction of the lead, carrying down with it.
the silver, the sulphur and oxygen combining and passing off as SO₂, other
bases than silver and lead present such as zinc, being volatilised, and the
slag skimmed off, the metallic silver-carrying lead being drawn off as it.
accumulates.
b.) Where argentiferous ores containing blende are to be treated, the first.
calcination of the said argentiferous blende to the condition of an oxide,.
and the addition thereto of sulphide of lead (galena) in a reverberatory
furnace, when the sulphur and oxygen combining according to the following.
equation―
SO, 2 Zn + Pb
2 ZnO + Pbs
=
which effects the metallic reduction of the lead, which will be alloyed with:
the silver, and of the zinc, which latter will be volatilized, either as a metal
or as an oxide, according to the atmosphere of the furnace and may be.
conveniently collected as either.
rd. As a specific process for the treatment of haloid (i.e. chloride, bromide, or-
ide) argentiferous ores, by mixing with said ores litharge and galena in the-
portion of two of litharge to one of galena in an oxidising reverberatory furnace,.
Order that metallic lead may be produced by the well known re-action between.
O and PbS simultaneously with the decomposition of the aforesaid haloids by
action with the re-acting mixture, resulting in haloid compounds of lead which.
atilize, and metallic silver which alloys with reduced lead, owing to the presence
an atmosphere of sulphur gas and the superior affinity of silver for sulphur-
ereby the loss of silver is obviated.
D 14th C A 1001
FELL & WILDING,
1, Queen Victoria Street, London, E.C., Agents for the Applicant..