IMPROVEMENTS IN THE TREATMENT OF SULPHO-ANTIMONIOUS AND SULPHO-ARSENIC GOLD AND SILVER ORES
Year: 1879

page_text: LETTERS PATENT to Walter Alfred Barlow, of 6, St. Paul's Churchyard,
London, Patent Agent and Engineer, for the Invention of "IMPROVEMENTS IN
THE TREATMENT OF SULPHO-ANTIMONIOUS AND SULPHO-ARSENIC GOLD AND
SILVER ORES." A communication from abroad by Charles de Vauréal, of Paris,
France
Sealed the 14th May 1880, and dated the 15th November 1879.
PROVISIONAL SPECIFICATION left by the said Walter Alfred Barlow at the
Office of the Commissioners of Patents on the 15th November 1879.
WALTER ALFRED BARLOW, of 6, St. Paul's Churchyard, London, Patent Agent
and Engineer. "IMPROVEMENTS IN THE TREATMENT OF SULPHO-ANTIMONIOUS AND
SULPHO-ARSENIC GOLD AND SILVER ORES." A communication from abroad by
Charles de Vauréal, of Paris, France.
Up to the present time many difficulties have been found in extracting gold and
silver from complex sulphurous ores.
These difficulties arise from,―
(1). The great affinity of arsenic and antimony for gold and silver, which causes
part of the precious metals to remain in combination with arsenic and antimony
and consequently divided.
(2). The volatility of arsenic and antimony which stimulates volatilization and
the loss of a notable quantity of the precious metals.
(3). The necessity of treating these ores with rich oxidized ores in order to
diminish the losses.
The process which is the subject of the present Invention permits of the
extraction of gold and silver from complex sulphurous ores in an economical
manner, and in such way that the quantities of precious metals obtained are greater
or at least equal to those ascertained by assaying.
This process is applicable in a general manner to all sulpho-arsenic and sulpho-
antimonious ores, and more especially to the following:-
Freieslebenite, myargyrite, panabase, polybasite, psaturose, pyrargyrite, prou-
stite. etc.

page_text: The process consists of the following:-The ore is ground by any well known
method and brought to a state of division as fine as possible.
When it is in this pulverised state it is submitted to a series of operations for
the purpose of eliminating successively the arsenic copper and antimony.
This succession of operations is one of the essential characteristics of this
Invention, and the order in which this takes place is not unimportant.
The first operation is to eliminate the arsenic, and to do this the following
operation takes place
The finely ground ore is placed in a gas retort and is heated to a dull red
heat.
A movable stirrer parallel to the axis of the retort which is capable of rocking
for about a quarter of a circle is employed for purpose of continually disturbing
and changing the material at the surface, but without lifting the particles. At the
same time a current of hydrogen gas is passed into the retort.
The sulphurets of arsenic, of antimony, and of silver, will be reduced in presence
of the bydrogen and form hydrosulphuric acid, and the arsenic is distilled.
These products are received into a chamber where the arsenic remains, and the
hydrosulphuric acid is carried into a purifier formed with divisions dipping into
a chalk bath. The excess of hydrogen is conducted into a second retort parallel,
where it is rinsed in a similar manner for the reduction of other ore.
As this excess which is necessary for eliminating the last traces of arsenic is
only produced towards the end of the operation, the work must be carried on
Buccessively in the different retorts. During the reduction of the ores by the
hydrogen a notable quantity of arsenicated bydrogen is produced, and in order to
destroy this poisonous gas care is taken at the mouth of the purifier, which has
absorbed the hydrosulphuric gas, to direct the residual gas which cannot be
absorbed in the furnace where it will be burned.
This first treatment as will be seen depends essentially upon the action of the
hydrogen as a reducing agent. The use of the hydrogen in order to produce the
desulphuration of the ores and to permit of the throwing off of the arsenic by
distillation is quite new, and is intended to be claimed as one of the important
elements of this process. The hydrogen may be produced in any well known or
desired manner, but it is preferred to use for the purpose the well known process of
the reaction of steam upon iron.
The ore thus reduced by the hydrogen takes the form of an agglomerate
resembling cake. It contains sulphuret of copper, which has not been reduced by
the hydrogen in the first operation on account of the heat at which the operation
is carried out not being sufficient, some reduced antimony, and some antimonial
silver along with the gangue.
The ore is crushed in a crusher and then roasted in a reverberatory furnace
arranged in such manner as to prevent a sudden excessive heating, and that the
flames be as oxidizing as possible. Care must be taken that the temperature
of the mass does not exceed a dull red heat.
This operation transforms the sulphuret of copper into oxide of copper and into
sulphate of copper, and there is thus produced antimonious acid and some
antimoniate of oxide of antimony. This last salt is not soluble in water nor in
diluted sulphuric acid; consequently the roasted regalus is treated by a cold
solution of sulphuric acid of 12° density, wherein the oxide of copper will be
dissolved, and this solution treated by iron precipitates the copper.
This washing may be methodically made in suchwise that a less dense acid
liquor is brought upon the richest roasted regulus. The residue is thus freed from
copper and is submitted to a water washing, and then treated by concentrated
hydrochloric acid in a closed vessel lined with lead, which transforms the
antimoniate of antimony into oxychloride of antimony and is then run off.
The operation may be arranged in such manner as to effect methodical washings,
which will give concentrated solutions of oxychloride of antimony, which is further

page_text: treated in order to extract the antimony, or to make the antimonius vermillion,
and the residue will contain all the silver in the form of chloride.
In this state it is suitable for amalgamation, or it may be treated by bisulphite
of soda, which completely dissolves the chloride of silver obtained in the humid
way.
The residue may also be treated by protoxide of lead, but then it is important to
dechloruret the silver by a chalk bath, or a washing of potash with a small
quantity of molasses; this operation is carried out at a temperature of 100°
centigrade.
The extraction of the precious metals either by the humid way or the dry way.
By the Humid Way. If it is required only to extract silver, then the bi-
sulphide of soda is employed. When on the contrary it is required to extract both
gold and silver, the operation is carried out by amalgamation. If the dechloruration
of the silver, which is indispensible by the dry way, is carried out, the residue may
still be treated in a cast iron boiler by boiling bot sulphuric acid, the sulphate of
silver is then reduced by copper.
By the Dry Way.-The dechlorurated residue is mixed with one half part of
mixed litharge and pulverized charcoal, in the proportion of 1 part by weight of
charcoal to 24 parts of litharge, and this mixture is cast with lead. During the
scorification or slaging the scoria must be agitated with green-wood, and near
the termination of the treatment there is added a small quantity of iron for the
purpose of reducing the excess of oxide of lead which is in the scoria, which is
then run off and replaced by a new quantity of the material to enrich the lead
bath. This last is treated by zinc or cupellation. In the case of a calcareous or
dolemitic gangue, the unroasted ore before reduction by hydrogen ought to be
washed in weak hydrochloric acid.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Walter Alfred Barlow in the Great Seal Patent Office on the 15th
May 1880.
WALTER ALFRED BARLOW, of 6, St. Paul's Churchyard, London, Patent Agent
and Engineer. "IMPROVEMENTS IN THE TREATMENT OF SULPHO-ANTIMONIOUS AND
SULPHO-ARSENIC GOLD AND SILVER ORES." A communication from abroad by
Charles de Vauréal, of Paris, France.
Up to the present time many difficulties have been found in extracting gold and
silver from complex sulphurous ores.
These difficulties arise from,-
(1). The great affinity of arsenic and antimony for gold and silver, which causes
part of the precious metals to remain in combination with arsenic and antimony,
and consequently lost in the amalgamation.
(2). The volatility of arsenic and antimony which stimulates volatilization and
the loss of a notable quantity of the precious metals.
(3). The necessity of treating these ores with rich oxidized ores in order to
diminish the losses.
The process which is the subject of the present Invention permits of the
extraction of gold and silver from complex sulphurous ores in an economical
manner, and in such way that the quantities of precious metals obtained are greater
or at least equal to those ascertained by assaying.
This process is applicable in a general manner to all sulpho-arsenic and sulpho-
antimonious ores, and more especially to the following:--Freieslebenite, myargyrite,
panabase, polybasite, psaturose, pyrargyrite, proustite, etc.
The process consists of the following:-
The ore is ground by any well known method and brought to a state of division
as fine as possible.
When it is in this pulverised state, it is submitted to a series of operations for
the purpose of eliminating successively the arsenic, copper, and antimony.
This succession of operations is one of the essential characteristics of this
Invention, and the order in which this takes place is not unimportant.
The first operation is to eliminate the arsenic, and to do this the following
operation is effected :—
The finely ground ore is placed in a gas retort and it is heated to a dull red heat.
A movable stirrer parallel to the axis of the retort which is capable of rocking
for about a quarter of a circle is employed for purpose of continually disturbing and
changing the material at the surface, but without lifting the particles, and at the
same time a current of hydrogen gas is passed into the retort. The sulphurets of
arsenic, of antimony, and of silver will be reduced in presence of the hydrogen and
form hydrosulphuric acid, and the arsenic is distilled.
These products are received into a chamber where the arsenic remains, and the
hydrosulphuric acid is carried into and condensed in a purifier formed with
divisions dipping into a chalk bath.
The excess of hydrogen is conducted into a second parallel retort, where it is
re-used in a similar manner for the reduction of the ore.
As this excess which is necessary for eliminating the lost traces of arsenic is only
produced towards the end of the operation, the work must be carried on successively
in the different retorts. During the reduction of the ores by the hydrogen a
notable quantity of arsenical hydrogen is produced, and in order to destroy this
poisonous gas care is taken at the mouth of the purifier, which has absorbed the
hydrosulphuric gas, to direct the residual gas which can not be absorbed into the
furnace where it will be burned.
This first treatment as will be seen depends essentially upon the action of the
hydrogen as a reducing agent. The use of the hydrogen in order to produce the
desulphuration of the ores and to permit of the throwing off of the arsenic by

page_text: distillation quite novel, and is intended to be claimed as one of the important
elements of this process.
The hydrogen may be produced in any well known or
desired manner, but it is preferred to use for the purpose the well known process
of the reaction of steam upon iron.
The ore thus reduced by the hydrogen takes the form of an agglomerate
resembling coke, which contains sulphuret of copper, which has not been reduced by
the hydrogen in the first operation on account of the heat at which the operation
is carried out not being sufficient, some reduced antimony, and some antimonial
silver along with the gangue.
The ore is crushed in a crusher and then roasted in a reverberatory furnace
arranged in such manner as to prevent a sudden excessive heating, and that the
flames be as oxidizing as possible. Care must be taken that the temperature of
the mass does not exceed a dull red heat.
This operations transforms the sulphuret of copper into oxide of copper and into
sulphate of copper, and there is thus produced antimonious acid and some antimoniate
of oxide of autimony. This last salt is not soluble in water nor in diluted sulphuric
acid, and consequently the roasted regulus is treated by a cold solution of sulphuric
acid of 12° density, wherein the oxide of copper will be dissolved, and this solution
treated by iron precipitates the copper. There may also be employed the ordinary
sulphuric acid of commerce of 66° density, in which case a development of heat is
produced during the reaction.
This washing may be methodically done in such wise that a less dense acid
liquor is brought upon the richest roasted regulus. The residue is thus freed from
copper and is submitted to a water washing, and then treated by a concentrated
hydrochloric acid in a closed vessel lined with lead, which transforms the
antimoniate of antimony into oxychloride of antimony which is then run off.
The operation may be arranged in such manner as to effect methodical washings,
which will give concentrated solutions of oxychloride of antimony, which is further
treated in order to extract the antimony or to make antimonious vermillion, and
the residue will contain all the silver in the state of chloride.
In this state it is suitable for amalgamation, or it may be treated by bisulphite
of soda, which completely dissolves the chloride of silver obtained in the humid
way.
The residue may also be treated by protoxide of lead, but then it is important to
dechlorurate the silver by a chalk bath, or a washing of potash with a small
quantity of molasses; this operation is carried out at a temperature of 100°
centigrade.
The extraction of the precious metals is effected either by humid way or the dry
way.
By the Humid Way.-If it is required only to extrat silver, then the bi-
sulphite of soda is employed. When on the contrary it is required to extract both
gold and silver, the operation is carried out by amalgamation. If the dechloruration
of the silver, which is indispensible by the dry way, is carried out, the residue may
still be treated in a cast iron boiler by boiling hot sulphuric acid, the sulphate of
silver is then reduced by copper.
By the Dry Way.-The dechlorurated residue is mixed with one half part of
mixed litharge and pulverized charcoal in the proportion of 1 part by weight of
charcoal to 24 parts of litharge, and this mixture is cast with lead; during the
scorification or slagging the scoria must be agitated with green-wood, and near the
termination of the treatment there is added a small quantity of iron for the purpose
of reducing the excess of oxide of lead which is in the scoria, which is then run off
and replaced by a new quantity of the mixture to enrich the lead bath. This last
is treated by zinc or cupellation. In the case of a calcareous or dolomitic gangue
the unroasted ore before reductiou by hydrogen ought to be washed in weak
hydrochloric acid.
It has been endeavoured to perfect the treatment by the dry mode in view of
the simultaneous extraction of the silver and gold, the researches having been

page_text: principally with the object of economising the acids and simplifying the means
employed.
These researches have resulted in the discovery of the series of operations
hereinafter described which are claimed hereunder.
First Operation. The crushed ore is pulverised with 10 to 20% of galena or
sulphuret of lead according to its antimonious quality, and 8 to 10% of chloride
of sodium, then it is reduced by the hydrogen at a dark red heat. The sulphuret
of arsenic is distilled; the sulphurets of lead, silver, and antimony are reduced in a
great degree, the lead, antimony, and the precious metals forming an alloy partly
mixed with the mass.
Second Operation.—The reducing action of the hydrogen is then replaced by the
oxidizing action of the air. This roasting is done in the same apparatus (gas
retort) and at a low temperature.
Third Operation. After this roasting the temperature is raised to promote the
fusion of the chloride of sodium and the reaction of the sulphates upon this salt.
It is distilled from the chloride of antimony which is condensed.
Fourth Operation.-Vent is given to the matters in fusion by receiving them in
cast iron forms, where they separate themselves in a metallic bulb and in a mixture
of chlorides; these last with the addition of salt are reused in the course of the
successive treatment of new minerals. The matts which remain in the retort are
taken out and suddenly cooled by immersion.
Fifth Operation. These matts are afterwards treated by the dry method for
copper, or by the humid method after grinding and roasting; in this latter case
their sulphatisation is completed in an apparatus for lixiviation, where the
sulphurous acid from the roasted matters with excess of air is condensed.
Sixth Operation. The metallic alloy containing the precious metals and
antimony is scorified at a low temperature and tested.
Having thus described the nature and particulars of the said Invention
I claim,-
First. The hereinbefore specified treatment of sulpho-arsenic and sulpho-
antimonious ores according to the following operations, viz. :-(a), elimination of
the arsenic; (b), elimination of the copper; (c), elimination of the antimony, as set
forth.
Second. The use of hydrogen gas as reducing agent of the sulphurets contained
in the ores, as set forth.
Third. The process of treatment above described for seperating the arsenic by
distillation.
Fourth. The process of treatment above described for seperating the copper by
means of a bath of sulphuric acid in solution.
Fifth. The process of treatment above described for eliminating the antimony by
means of methodical washings by concentrated hydro-chloric acid.
Sixth. The process of treatment above described for collecting the precious
metals by the dry way" or by the "humid way."
<
Generally. The application of all the above processes for seperating the precious
metals from the gangue remaining only in the residue obtained after the elimination
above set forth, and the application of the process to all ores containing sulphuret
of arsenic and of antimony.
In witness whereof, I, the said Walter Alfred Barlow, have hereunto set
my hand and seal, this Fourteenth day of May, in the year of our Lord
One thousand eight hundred and eighty.