Improvements relating to the Extraction of Gold, Silver, and Lead from Substances Containing the same and to Apparatus therefor.
Year: 1889

page_text: Date of Application, 1st Jan., 1889
Complete Specification Left, 5th Oct., 1889-Accepted, 9th Nov., 1889
PROVISIONAL SPECIFICATION.
Improvements relating to the Extraction of Gold, Silver, and Lead
from Substances Containing the same and to Apparatus therefor.
1, Albert BerwICK CUNNINGHAM, of 85, Arlington Street, Islington, in the
County of London, Gentleman, do hereby declare the nature of this invention (partly
a communication to me from abroad by HENRY HAVEMANN of
Paris,
France, Merchant, and partly the result of my own invention) to be as follows :-
My invention relates to the extraction of gold, silver and lead from ores or substances
containing the same and to apparatus therefor.
My said invention consists essentially in heating the ore or substance from which
metal is to be extracted with a caustic alkali and if such ore or substance contains no
lead with a proportion of galena or other substance containing lead.
In assaying compounds containing lead the use of Carbonate or bi-carbonate of
Soda has long been known. Metallic iron has also been added for the purpose of
preventing the formation of a double Compound of Sodium and lead. The quantity
of carbonate or bi-carbonate required however generally exceeds twice the weight of
the Compound under treatment and the heat necessary to obtain a reduction in
presence of an alkaline carbonate is high.
By my invention I not only obviate any necessity for the addition of iron, but also
decrease the proportion of alkali relative to the weight of the metallic Compound
under treatment, whereby I obtain the following advantages over the old process,
videlicet, firstly, the reduction of expense hy reason of the relatively small quantity of
alkali used; secondly, rapidity in attaining results owing partly to the fact that caustic
alkali sets a moro vigorous reaction than Carbonates and partly because the fusion
of caustic takes place at a far less heat than when Carbonates are used; and, thirdly,
because by the use of caustic alkali I approach more nearly in metallic results (gold,
silver and lead) to the quantities determined by wet analysis than by any other known
dry method of estimating the quantities of the metals referred to in a given substance
containing them.
Not only does my invention provide an improved assaying process but also the
ineans of obtaining more complete results when treating ores or substances containing
the metals named, than any other so called smelting processes now known and practised
commercially.
According to my invention the metallic compound to be treated is brought in
contact with the required proportion of caustic alkali (hydrate of sodium or potassium).
preferably in an iron vessel and submitted to the action of heat or on the hearth of an
open reverberatory furnace provided with an iron bottom and sides (cast iron plates) or
lined with fused caustic bottoms or by any other lining calculated to resist the action
of caustic alkali.
The vessel or smelting pot above referred to is advantageously made of cast iron
owing, first, to the comparatively low heat necessary for the operation, second, to the
form of furnace employed in "connection with it, and, third, to the mode of firing
which is that of slow combustion (coke or charcoal being the fuel) the admission of air
being so restricted that no oxidizing flame is created and the stoking so controlled that
no fuel touches the exterior of the pot or vessel.
The iron vessel or smelting pot can be placed on a brick pier which is constructed
within a circular furnace, the walls being gathered in at the top and provided with
flues, the inlets to which are chequered. The fuel is introduced in such quantities as
only to reach up to the level of the pier on which the vessel rests. During operation
the ash pit (also circular) is closed, with the exception of a very small inlet for
admitting air for maintaining combustion. The ashes are withdrawn by means of

page_text: channels or tunnels in the walls of the furnace. Both fuel and mineral are fed from
above.
In order to modify the corrosive effects on the interior surfaces of the vessel or pot
which occur in treating sulphides, I use an iron lining which consists of a number of
concentric cast iron rings placed one on top of the other and collectively following the
internal form of the vessel. This lining is easy of adjustment and replaced without
difficulty whenever occasion arises.
The ore or compound to be treated is placed in the pot previously heated to redness
and on it is placed the Caustic Alkali.
Or the Alkali may first be introduced and on it the mineral.
Or the Compound and the Alkali may be mixed in a pulverized condition and then
placed in the smelting pot.
Owing to the extreme fusibility of the Caustic alkali an active evolution will take
place within a few minutes of the introduction of the materials into the pot. In a
short space of time, varying according to the nature of the metallic substances, the
reduction or separation is complete and the charge is drawn off through a discharge
pipe into a receiver of any convenient form.
The lead (and with it any gold or silver present) falls to the bottom and on it rests
the slag composed of compounds of the matrix and alkali.
After solidifying, the slag and the metal are separated, the latter being found as a
solid ingot at the bottom of the mass.
No more caustic alkali should be used than sufficient for the reduction or separation
of the lead and silver or gold from the other elements or impurities present in the
matrix.
This is advisable in order to avoid the formation of additional alkaline compounds.
In cases where a higher liquidity is required than obtained by the caustic necessary
for reduction or separation it may be found advantageous to employ an addition of
common salt (chloride), but then the reduction or separation should be allowed to take
place first and the salt afterwards introduced.
The same treatment can be carried out in an open reverberatory furnace or in a
furnace with a divided hearth, using slow combustion in the latter instance.
In treating gold or silver ores which do not contain sufficient lead, the operation is
effected by adding enough lead ore or compound to make up the deficiency.
The gold, silver and lead are separated by cupellation or by any other suitable
process.
The slags produced are as above stated compounds of the matrix and alkali and are
soluble. Any insolubles fall to the bottom by lixiviation. This provides an easy
means of recovering any lead or unreduced lead ore which may have become entangled
with the slag.
The liquor may be profitably employed in the production of caustic alkali by any
of the well-known methods.
Dated the 1-11
T
1000
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.
COMPLETE SPECIFICATION.
Improvements relating to the Extraction of Gold, Silver and Lead
from Substances Containing the same and to Apparatus therefor.
1, ALBERT BERWICK CUNNINGHAM, of 85, Arlington Street, Islington, in the
county of London, Gentleman, do hereby declare the nature of this invention (partly
a communication to me from abroad by HENRY HAVEMANN, of 5 Passage Saulnier,
Paris, in the republic of France, Merchant, and partly the result of my own invention)
and in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement :-
This invention relates to the extraction of gold, silver and lead from ores or
substances containing the same and to apparatus therefor.

page_text: The said invention consists essentially in heating the ore or substance from which a
metal is to be extracted with caustic alkali and if such ore or substance contains no
lead, with a proportion of galena or other substance containing lead.
In assaying compounds containing lead the use of carbonate or bi-carbonate of soda
has long been known. Metallic iron has also been added for the purpose of preventing
the formation of a double compound of sodium and lead. The quantity of carbonate
or bi-carbonate required, however, generally exceeds twice the weight of the compound
under treatment, and the heat necessary to obtain a reduction in presence of an
alkaline carbonatè is high.
By this invention not only is any necessity for the addition of iron obviated but the pro-
portion of alkali required relative to the weight of the metallic compound under treatment
is decreased whereby the following advantages over the whole process are obtained vis:-
firstly, the reduction of expense by reason of the relatively small quantity of alkali
used; secondly, rapidity in obtaining results owing partly to the fact that caustic
alkali sets up a more vigorous reaction than carbonates, and partly because the fusion
of caustic alkali takes place at a far less heat than carbonates; and thirdly, nearer
approach in metallic results (gold, silver and lead) to the quantities determined by wet
analysis than by other so called smelting processes now known and practised
commercially.
According to this invention the metallic compound to be treated is brought in
contact with the required proportion of caustic alkali (hydrates of sodium or potassium)
preferably in a cast iron vessel, (although wrought iron may be used) and submitted
to the action of heat but the treatment may be effected on the hearth of an open
reverberatory furnace provided with an iron bottom and sides (say cast iron plates) or
lined with fused caustic bottoms or any other lining calculated to resist the action of
caustic alkali; or in a furnace with a divided hearth using slow combustion in the
latter instance.
Apparatus suitable for carrying out this invention is illustrated in the accompanying
drawing, in which,-
Figure 1 is a sectional elevation; and,
Figure 2a sectional plan, the section being taken on the line e figure 1.
a is the iron vessel or smelting pot and b is a spout formed at the lower part of the
same. This pot is mounted on a pier c and is enclosed in a circular chamber d, the
walls e, e of which are gathered in at the top as shown.
fis a circular furnace which is formed around the pier c, and g, g are a number of
openings which communicate with a flue the latter leading into a chimney or other
flue i.
jis an ash-pit beneath the furnace f, and kk are a series of openings or passages
for affording access to the said ash-pit for cleaning the same.
is a plate which covers the top of the apparatus, and m, m are openings formed in
the said plate and provided with covers to allow the introduction of fuel into the
furnace.
In the operation of this apparatus a slow burning fuel such as coke or charcoal is
employed, the fuel being introduced in such quantities as only to reach up to the level
of the pier on which the vessel rests; and the admission of air is 50 restricted that no
oxidizing flame is created and the stoking so controlled that no fuel touches the
exterior of the vessel.
In order to modify the corrosive effects on the interior surfaces of the vessel or pot,
which occur in treating sulphides, an iron lining is used which consists of a number of
cast iron rings n placed one on top of the other and adapted to the internal form of the
vessel. This lining is easy of adjustment and replaced without difficulty whenever
occasion arises.
The ore or compound to be treated is placed in the pot previously heated to redness
and on it is placed the caustic alkali in a proportion of say 25 per cent. more or less
to the quantity of ore or substance under treatment, the proportion of alkali varying
according to the nature of the substance. For example, in treating common galena
I have found that a proportion of 30 per cent. by weight of caustic alkali gives good

page_text: results. If desired, the alkali may first be introduced and then the mineral, or the
compound and the alkali may be mixed in a pulverized condition and then placed in
the smelting pot.
"
Owing to the extreme fusibility of the caustic alkali an active ebullition will take
place within a few minutes of the introduction of the materials into the pot. In a short
space of time, varying according to the nature of the metallic substances, the reduction
or separation is complete and the charge is drawn off through the discharge pipe b
into a receiver of any convenient form.
The lead (and with it any gold or silver present) falls to the bottom, and on it rests
the slag composed of compounds of the matrix and alkali.
After solidifying, the slag and the metal are separated, the latter being found as a
solid ingot at the bottom of the mass.
No more caustic alkali should be used than suffices for the reduction or separation
of the lead and silver or gold from the other elements or impurities present in the
matrix, this being advisable in order to avoid the formation of additional alkaline
compounds.
In cases where, owing to the small proportion of lead relative to the matrix, it is
advisable to reduce the mass to a higlier state of liquidity than can be obtained by the
use of the actual quantity of caustic alkali necessary for the reduction or separation,
.it is advantageous, in order to avoid the necessity for using a larger quantity of alkali,
to employ an addition of common salt (chloride of sodium) but then the reduction or
separation should be allowed to take place first, and the salt afterwards introduced.
In treating ores or substances containing gold or silver, and which do not contain
sufficient lead the operation is effected by adding enough lead ore or compound to
make up the deficiency.
The gold, silver and lead are separated by cupellation or by any other suitable
process.
The greater portion of the slag produced is, as above stated, compounds of the
matrix and alkali and is soluble, if this slag is lixiviated the insoluble portions thereof
precipitate, thus providing easy means of recovering any metal or unreduced ore
which may have become entangled with the slag.
The liquor may be profitably employed for the production of caustic alkali by any
of the well known methods. Although the process hereinbefore described is for the
extraction of gold, silver and lead on a commercial scale, it is to be understood that
the said process is equally applicable for effecting assays of ores or substances con-
taining such metals.
Having now particularly described and explained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what 1
claim is :-
(1) The use of caustic alkalies, substantially as hereinbefore described, for the
reduction and extraction of gold, silver and lead from substances containing the same.
(2) The extraction of gold and silver from ores or substances containing the same
by mixing such ores or substances with compounds containing lead and treating the
mixture with caustic alkali, substantially as described.
(3) The manufacture and use of the improved apparatus herein before described and
illustrated in the accompanying drawing for the purpose specified.
Dated the 5th
1000
G. F. REDFERN & Co.,
4, South Street, Finsbury, London, Agents for the Applicant.