A New or Improved Process for Extracting Gold, Silver, and other Metals from Refractory Ores, Sands, and Residues.
Year: 1888

page_text: Date of Application, 21st Aug., 1888
Complete Specification Left, 21st May, 1889-Accepted, 22nd June, 1889
PROVISIONAL SPECIFICATION.
A New or Improved Process for Extracting Gold, Silver, and other
Metals from Refractory Ores, Sands, and Residues.
I, Monsieur le Comte EDOUARD DE ROTTERMUND of Bludow, Volhynia, in the
Empire of Russia, Landowner, do hereby declare the nature of this invention to be as
follows:-
The ores, sands or residues after being crushed are roasted, with or without
common salt, according to circumstances, as may be found necessary, in a properly
constructed furnace, so arranged that the resulting sulphurous acid and hydrochloric
acid and the dust are collected in properly adapted chambers, as will be well under-
stood. For this purpose any roasting process which will effect this can be adopted
but by preference I would use the Munktell furnace.
The ores, sands or residues, having been properly roasted, are placed, preferably
warm from the furnace, in vats, barrels, or other suitable receptacles, which may be
of any size or shape, as may be found most convenient for the ores, sands or residues
under treatment, and preferably arranged so as to be self-dumping.
They are constructed with false bottoms, which are pierced with holes about 7 to
8 millimetres in diameter, and both receptacles and false bottoms are constructed
entirely of, or lined with, some material not attacked by chlorine. I prefer the vats
and false bottoms to be made of wood. Above the false bottoms there is placed a
layer of small stones or other material to act as a filter. The sizes of the vats and
furnace should be so adapted to each other as to allow the processes to be continued
without interruption in order to save time and expense.
The ores, sands or residues in the vats are submitted to the action of dilute sulphuric
or muriatic acid of a specific gravity of 1.01 or thereabouts, or other diluted acid,
warmed preferably by steam to a temperature of about 140 degrees Fahrenheit. This
acid solution transforms the protoxides and salts at minimum of oxidation into oxides
and salts at maximum of oxidation. The acids used in this part of the process may
be those obtained from the roasting of the ores, sands or residues. I would use
muriatic acid in preference to sulphuric acid when obtainable, because this avoids the
formation of sulphate of lime in a succeeding process.
The liquid, after the salts are dissolved, generally at the expiration of from 2 to
5 hours, is allowed to run into a lower vat containing scrap iron by which the contained
copper, silver &c., are precipitated. The sulphate of iron so obtained may be used in
a subsequent part of the process. The operation is finished so soon as the effluent
liquid ceases to affect permanganate of potash.
The ores, sands or residues are then leached with cold water to reduce the tempera-
ture to about 60 degrees Fahrenheit, so as to avoid a useless loss of chlorine.
Two casks or other suitable vessels composed of wood or some other material not
affected by chlorine and placed above the vats are now filled, the one preferably with
dilute hydrochloric acid of specific gravity 1.003 or other specific gravity, as may be
found most suitable, and the other with a solution of chloride of lime in the proportion
of 0.7 to 1 gramme of chloride of lime per litre of water.
The chloride of lire and the hydro-chloric acid may be replaced by any other
solutions capable of giving out chlorine.
The two casks should be of about equal capacity and of such size as is proportionate
to the quantity of ore to be treated. For vats holding 800 kilogrammes of roasted
ores, sands or residues, the casks should hold about 170 litres each.
The two solutions are now allowed to reach the vat in equal proportions by a
common pipe and to percolate through the inass of ores, sands or residues into
a receptacle beneath. The nascent chlorine formed by the mixture of these two
a

page_text: solutions combines with the gold which has by the previous process been placed in
the best condition for such combination and a soluble chloride of gold is formed.
The finer the gold in the ores, sands or residues, the quicker is the operation.
The progress of the chlorination can be continuously tested by means of chloride of
tin, which gives a precipitate well known as purple of Cassius. At first the reaction
is weak, then greater, attains a maximum, and then diminishes. When the reaction
is almost insensible the operation is stopped. It is thus seen that the operation of
chlorination is entirely under the control of the operator, thereby avoiding any
unnecessary loss of time or of chlorine.
The liquid collected contains chloride of gold and a little chloride of silver, resulting
from the silver which has not been attacked in the preceeding process. The silver is
precipitated with a small quantity of iodate of potash and the silver may be obtained
by any known process.
The solution of chloride of gold is precipitated by any ordinary method, preferably
by the sulphate of iron obtained in a former part of the process and the precipitate so
formed is reduced to metallic gold in the usual manner.
D
31
COMTE E. DE ROTTERMUND.
By Harris & Mills,
23, Southampton Buildings, Agents.
COMPLETE SPECIFICATION.
A New or Improved Process for Extracting Gold, Silver, and other
Metals from Refractory Ores, Sands, and Residues.
I, Monsieur le Comte EDOUARD DE ROTTERMUND, of Bludow, Volhynia, in the
Empire of Russia, Landowner, 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, reference being had to the accom-
panying drawings, and to the figures and letters marked thereon:-
The invention is based on the extraction of gold by means of chlorine, and consists
of a new or improved process for the extraction of the precious and other metals from
refractory ores, sands, and residues, by an economical continuous operation, by which
such extraction is rendered more economical in point of time, material, and labor, and
more gold is extracted from the ores, sands, and residues, than by any other known
method, and ores, sands, or residues so treated, can be worked at a profit which could
not be so worked by any other method. Experience. has shown that chlorine is
unable to extract the gold from the ores, if the former is combined with metallic
sulphurets, unless these are rendered innocuous, that is, removed, prior to the process
of extraction of the gold. According to my invention, I prepare the ores in such a
manner that the gold becomes accessible to the influence of the chlorine and that it
alone attracts the action of the chlorine, and the process is so conducted that only
sufficient chlorine is employed as may be theoretically requisite to release the gold.
Moreover, I use the chlorine in nascent state, namely, in its fullest strength, so that
very weak solutions of chlorine are and can be employed, and the process can there-
fore be carried on in open vessels, without causing annoyance to the workmen, and
without loss of chlorine. Another entirely new feature of my process is, that by
chemical means, I only extract the most finely distributed gold, or such combined
gold as could not be obtained by mechanical means; in other words, I only expose
the ore so long to the reaction of the chlorine as to extract therefrom the very finest
gold. After that, the gold which is sufficiently coarse grained for its specific
gravity to come into play, is extracted by mechanical means; in fact, this operation
taking place only after washing and chlorinating, the gold is entirely free of super-
ficial impurities. All loss of gold is avoided, and the process is one of the. most
complete and economical of the kind hitherto known.
The process may be divided into the five following principal operations.
1. Roasting

page_text: The extraction o the secon
3. The removal of the protoxide salts.
4. The extraction of the fine gold, and
5. The final washing of the residue in order to collect the coarse gold remaining.
Particular attention is paid to the roasting of the ores, so that the metallic
sulphurets may be separated in any easily reducible form; for instance, if the ore
contains a great deal of zinc, it is treated when being roasted with common salt, with
anhydrate neutral Ferri-sulphate; if a considerable quantity of antimony and arsenic
is present, then the ores are sometimes submitted to an oxidising roasting process,
before they are roasted by common salt; and so on, according to the influence
which the secondary metals may exercise on the reduction of the gold.
The process of roasting consists of two operations, viz., warming the charge up to
the temperature required for eliminating the sulphur, then in the chloridising, roasting
and burning at a moderate temperature, without too strong a draught, and may be
conducted in a properly constructed furnace, so arranged that the metallic vapors are
condensed and the resulting sulphurous acid and hydrochloric acid and the dust, are
collected in properly adapted chainbers, as will be well understood. For this purpose
any roasting process which will effect this can be adopted, but by preference I would
use the Munktell furnace.
Figures 1 and 2 are two elevations drawn at right angles to each other, and
Figure 3 is a plan of the apparatus I employ in the treatment of the ores after the
roasting process.
The ores, sands, or residues, having been properly roasted, are placed, preferably
warm from the furnace, in vats or barrels C or in other suitable receptacles, which
may be of any size or shape, as may be found most convenient for the ores, sands or
residues under treatment, and preferably arranged so as to be self-dumping.
9, 9, 9 represent the wheels and tipping apparatus, and 10 the rails upon which the
vat C is run underneath the shoot 11 for the roasted ores, sands or residues, and to
the dump shoot.
These vats or barrels C are constructed with false bottoms 7, which are pierced with
holes about 7 to 8 millimetres in diameter, and both receptacles and false bottoms are
constructed entirely of, or lined with, some material not attacked by chlorine. I prefer
the vats C and false bottoms 7 to be made of wood.
Above the false bottoms there is placed a layer 8 of small stones or other material
to act as a filter. The sizes of the vats C and furnace should be so adapted to each
other as to allow the processes to be continued without interruption in order to save
time and expense.
The ores, sands or residues in the vats C are submitted to the action of dilute
sulphuric or muriatic acid of a specific gravity of 1.01 or thereabouts, or other
diluted acid coming from the cask B and warmed, preferably by steam, to a tempera-
ture of about 140 degrees Fahrenheit.
Steam is supplied to the cask B by the steam pipe 15 and steam cock with short
hose 16.
This acid solution transforms the protoxides and salts at minimum of oxidation into
oxides and salts at maximum of oxidation. The acids used in this part of the process
may be those obtained from the roasting of the ores, sands or residues. I would use
muriatic acid when obtainable in preference to sulphuric acid, because this avoids the
formation of sulphate of lime in a succeeding process; as a substitute for acids,
bisulphate of soda may be employed, which is cheaper and easier for transport.
The liquid, after the salts are dissolved, generally at the expiration of from 2 to
5 hours, is allowed to run into a lower vat containing scrap iron, or other necessary
reactives, by which the contained copper, silver, &c., are precipitated. The sulphate
of iron so obtained may be used in a subsequent part of the process.
The operation is finished so soon as the effluent liquid ceases to affect permanganate
of potash.
The ores, sands or residues are then leached with cold water to reduce the tempera-
ture to about 60 degrees Fahrenheit, so as to avoid a useless loss of chlorine..

page_text: Two casks or other suitable vessels A B, composed of wood or some other material
not affected by chlorine, and placed above the vats C, are now filled, the one B
preferably with dilute hydrochloric acid of specific gravity 1.003, or other specific
gravity as may be found most suitable, or bisulphate of soda may be substituted for
the acids, and the other A with a solution of chloride of lime in the proportion
of 0.7 to 1% or 7 to 10 grammes of chloride of lime per litre of water.
The solution of chloride of lime is supplied to the cask A from the preparing tank
(not shown) by the conduit 1, and the dilute acid is supplied to the cask B from the
preparing tank (not shown) by the conduit ?.
The chloride of lime and the hydrochloric acid may be replaced by any other
solutions capable of giving out chlorine.
The two casks A and B should be of about equal capacity and of such size as is
proportionate to the quantity of ores, sands or residues to be treated. For vats C
holding 80 kilogrammes of roasted ores, sands, or residues, the casks A and B should
hold about 170 litres each.
The two solutions are now allowed to reach the vat C in equal proportions by a
common pipe 4, connected to the conduit 3, which receives the solutions from the
casks A and B through the cocks 5, and supplies them to the pipe 4 by means of the
plugs 6. These solutions percolate through the mass of ores, sands or residues in
the vat C into a receptacle c beneath.
The nascent chlorine formed by the mixture of these two solutions, combines with
the gold, which has by the previous process been placed in the best conditions for
such combination, and a soluble chloride of gold is formed, which is at once run off,
thereby avoiding the further contact of the said chloride of gold solution with the
ores, which would tend to reduce again to the metallic state the gold contained in the
said solution.
The finer the gold in the ores, sands, or residues, the quicker is the operation.
The progress of the chlorination can be continuously tested by means of chloride of
tin, which gives a precipitate well known as Purple of Cassius. At first the reaction
is weak, then greater, attains a maximum, and then diminishes. When the reaction
is almost insensible, the operation is stopped.
It is thus seen that the operation of chlorination is entirely under the control of the
operator, thereby avoiding any unnecessary loss of time or of chlorine, and that the
chloride of gold which is formed is at once run off. It must be understood that if
any coarse gold remains in the ores, sands or residues after treatment as above
described, it can be separated therefrom by mechanical means.
The liquid collected contains chloride of gold and a little chloride of silver, resulting
from the silver which has not been attacked in the preceding process. The silver is
precipitated with a small quantity of iodide of potash or with sulphuretted hydrogen,
and the silver may be obtained by any known process.
The solution of chloride of gold is precipitated by any ordinary method, preferably
by the sulphate of iron obtained in a former part of the process, and the precipitate
so formed is reduced to metallic gold in the usual manner.
If the auriferous ore under treatinent is found to contain a great quantity of silver,
it is necessary to mix it with common salt in sufficient quantity to obtain the complete
conversion of silver into chloride of silver. When the ore is not sulphurous, there is
added to it 5 to 10 per 100 of any pyrites before roasting. Afterwards the roasted
ore is washed with a concentrated solution, warm or cold, of common salt or hypo-
sulphite of soda. The chloride of silver dissolved, is treated by iodide of potash and
precipitated as an iodide of silver. The silver can be reduced into a metallic state by
pieces of metallic zinc.
Dis the cask for the copper solutions.
E is the cask for the gold solutions.
12 is a pipe for cold water, which supplies water, by the cock and short hose 13, to
the upper casks, and by the cock and long hose 14, to the lower casks D and E.
17 is a steam cock with long hose to supply steam to the lower casks. 18 is a cock
to convey solutions from ore vat C-into the conduit 19. 20 are conduits receiving

page_text: solutions from vat C and conveying them to the lower casks D E. 21 are cocks for
supplying solution from casks D. E to conduit 22, which conveys it to the pre-
cipitating tanks &c. 23 are plugs in conduit 19. 24 are water gates in conduits 1, 2
and 19, and 25 are troughs leading from cocks 21 of casks D to the conduit 22.
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 I
claim is :-
-
1. The new or improved process of extracting the precious and other metals from
refractory ores, sands, and residues, by an economical continuous operation, sub-
stantially as herein described.
2. The improved process for extracting gold, silver, and other metals, from
refractory ores, sands and residues, consisting in first roasting such ores, secondly,
submitting them, while warm, to the action of warmed dilute sulphuric or muriatic
acid, or to the action of other acid solution, thirdly, subjecting the resulting liquid to
the action of scrap iron or other necessary reactives, to secure precipitation of the
copper, silver &c., fourthly, leaching the effluent liquid with cold water to reduce the
temperature, and then introducing chlorine in the exact quantity necessary for its
combination with metals, without the necessity for employing air-tight or closed
vessels, and running off the chloride of gold as soon as it is formed, all as herein
described.
3. In a process for the separation and removal of gold, silver, &c., from refractory
ores, sands, and residues, the introduction of chlorine in the exact quantity for its
combination with metals, subsequently to the treatment, by roasting and by dilute
acids and leaching, of said ores, sands and residues, as and for the purpose
described.
4. The separation and removal of the salts of copper, silver, &c., from the ores,
sands, or residues, prior to chlorination, by the process of treatment by dilute
sulphuric, muriatic, or other acid, and leaching, thereby leaving the chlorine freer to
act on the gold only, thus saving loss of chlorine and time.
Dated this 21st day of May 1889.
MONSIEUR LE COMTE EDOUARD DE ROTTERMUND.
By Harris & Mills,
23, Southampton Buildings, London, Agents.