Improvements in and relating to the Extraction of Gold and Silver from their Ores..
Year: 1895

page_text: Date of Application, 27th Apr., 1895
Complete Specification Left, 24th Jan., 1896-Accepted, 25th Apr., 1896
PROVISIONAL SPECIFICATION.
Improvements in and relating to the Extraction of Gold and Silver
from their Ores..
I, ALBRECHT SCHMIDT, Dr. of Philosophy, Chemist, Müllerstr. 170, Berlin, N.
in the German Empire, do hereby declare the nature of this invention to be as
follows:-
My invention relates to the extraction of gold and silver from ores containing
one or both of these metals and further to new or improved solvents for gold and
silver.
The methods at present in use for the extraction of gold from ores are based
upon the treatment of the auriferous ores with weak or dilute solutions of cyanide
of potassium. Such extraction proceeds but slowly, more especially when the
gold is not finely distributed in the ore. Instead of cyanide of potassium the
cyanide of another alkali metal, such for instance as cyanide of sodium may be
employed.
It is known that by the addition of an oxydizing agent to the solution of
cyanide of the alkali metal, the dissolving of gold is accelerated. This method
has not been generally employed, because the cyanide of the alkali metal is
partially destroyed by the employed oxidizing agent; the process has therefore
not turned out a financial success. All oxidizing agents hitherto proposed for
improving and accelerating the dissolving or extracting of gold have an oxidizing
action on the extracting or dissolving agent, i.e. on the cyanide of the alkali metal,
thereby forming a cyanate; the corresponding portion of the cyanide is therefore
lost for the extracting process, whilst the corresponding portion of the oxidizing'
agent is lost for the oxidation of gold.
My invention is based upon the idea of accelerating the dissolving action of the
cyanide on gold or silver by a substance to be added, which has no deleterious'
action on the cyanide of the alkali metal.
I have discovered that all substances containing oxygen in a state not too
active, on the one hand, do not oxidize the cyanide of the alkali metal and therefore
do not convert such cyanide into cyanate, and on the other hand such substances
can furnish the oxygen necessary for dissolving gold and silver. I have found
that organic nitro-compounds and nitroso-compounds act in this manner and are
therefore adapted for this purpose.
If the nitro-compounds do not contain too many nitro-groups, such compounds
are without any action on the cyanide of the alkali metal; if however (as for
example in the case of picric acid) the nitro-compound contains a great number
of nitro-groups very loosely bound or in a highly active state, an action on
the cyanide of the alkali metal takes place, but these are only exceptional
cases.
The new process can be performed in the known manner with the employment
of cyanide of an alkali metal without any addition; it is only necessary that before
or during the extracting process an organic nitro-compound or nitroso-compound
or some of such compounds are added to the lixiviating solution of cyanide of the
alkali metal. I prefer to employ for the extraction a further addition of hydrate
or carbonate of an alkali or alkaline earth.
The characterized oxidizing agent may also be mixed (the substances or any one

page_text: or more of them being in a solid, dry, semi-dry or dissolved condition) with the
cyanide of the alkali metal preferably employing an addition of carbonate or
hydrate of an alkali or alkaline earth. Such mixture, especially, if the same has a
solid or dry or semi-dry form, can be stored, packed, shipped or transported.
Amongst the nitro-compounds and nitroso-compounds to be used according to my
invention, the following substances may be mentioned as examples, viz. :-Nitro-
benzol, nitrobenzolsulphonic acid and its salts, nitrophenol, binitrophenol, nitro-
naphthol, nitrophenolsulphonic acid and its salts, nitrosonaphthol, nitroglycerin,
chlorurated picrin, nitrañilin, nitranilinsulphonic acid and its salts. Other suitable
nitro-compounds or nitroso-compounds can, however, be employed if desired.
Deted the 27th day of April 1805
D. YOUNG & Co.,
11 & 12 Southampton Buildings, London, W.C.,
Agents for the Applicant."
D. YOUNG & Co.,
11 & 12 Southampton Buildings, London, W.C.,
Agents for the Applicant."
Improvements in and relating to the Extraction of Gold and Silver
from their Ores.
I, ALBRECHT SCHMIDT, Dr. of Philosophy, Chemist, Müllerstr. 170, Berlin, N.
in the German Empire, 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 :-
My invention relates to the extraction of gold and silver from ores containing
one or both of these metals and further to new or improved solvents for gold and
silver.
The methods at present in use for the extraction of gold from ores are based
upon the treatment of the auriferous ores with weak or dilute solutions of cyanide
of potassium. Such extraction proceeds but slowly, more especially when the
gold is not finely distributed in the ore. Instead of cyanide of potassium the
cyanide of another alkali metal, such for instance as cyanide of sodium may be
employed.
It is known that by the addition of an oxydizing agent to the solution of
cyanide of the alkali metal, the dissolving of gold is accelerated. This method
has not been generally employed, because the cyanide of the alkali metal is
partially destroyed by the employed oxidizing agent; the process has therefore
not turned out a financial success. All oxidizing agents hitherto proposed for
improving and accelerating the dissolving or extracting of gold have an oxidizing
action on the extracting or dissolving agent, i.e. on the cyanide of the alkali
metal, thereby forming a cyanate; the corresponding portion of the cyanide is
therefore lost for the extracting process, whilst the corresponding portion of the
oxidizing agent is lost for the oxidation of gold.
My invention is based upon the idea of accelerating the dissolving action of the
cyanide on gold or silver by a substance to be added, which has no deleterious
action on the cyanide of the alkali metal.
I have discovered that all substances containing oxygen in a state not too
active, on the one hand, do not oxidize the cyanide of the alkali metal and
therefore do not convert such cyanide into cyanate, and on the other hand such
substances can furnish the oxygen necessary for dissolving gold and silver. I
have found that organic nitro-compounds and nitroso-compounds act in this manner
and are therefore adapted for this purpose.
If the nitro-compounds do not contain too many nitro-groups, such compounds
are without any action on the cyanide of the alkali metal; if however (as for
example in the case of picric acid), the nitro-compound. contains a great number of

page_text: nitro-groups very loosely bound or in a highly active state, an action on the cyanide
of the alkali metal takes place, but these are only exceptional cases.
The new process can be performed in the known manner with the employment.
of cyanide of an alkali metal without any addition; it is only necessary that before
or during the extracting process an organic nitro-compound or nitroso-compound
or some of such compounds are added to the lixiviating solution of cyanide of the
alkali metal.
It is generally preferred to add such proportions of the nitro or nitroso
compounds that the lixiviating solution shall contain less than about 5 per cent. of
the same; about 1 per cent. or even less may be sufficient in most cases.
In
practice the definite proportions should be previously determined by trial with
small quantities. I prefer to employ for the extraction a further addition of
hydrate or carbonate of an alkali or alkaline earth. The amount of such.
addition depends upon the nature of the ores to be treated, .e. upon their more
or less acid character. Generally it has been found to be advantageous to add
such proportions of hydrate or carbonate of an alkali or alkaline earth as
correspond to 20 per cent. of the proportions of nitro- or nitroso compounds.
employed.
The characterized oxidizing agent may also be mixed (the substances or any one
or more of them being in a solid, dry, semi-dry or dissolved condition) with the
cyanide of the alkali metal preferably employing an addition of carbonate or
hydrate of an alkali or alkaline earth. Such mixture, especially, if the same has.
a solid or dry or semi-dry form, can be stored, packed, shipped or transported.
Amongst the nitro-compounds and nitroso-compounds to be used according to my
invention, the following substances may be mentioned as examples, viz. :-Nitro-
benzol, nitrobenzolsulphonic acid and its salts, nitrophenol, binitrophenol, nitro-
naphthol, nitrophenolsulphonic acid and its salts, nitrosonaphthol, nitroglycerine,
chlorurated picrin, nitranilin, nitranilinsulphonic acid and its salts. Other
suitable nitro-compounds or nitroso-compounds can, however, be employed if
desired.
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
A process for the extraction of gold and silver by means of cyanide of alkali
metal, characterized by the employment or addition of organic nitro- or nitroso-
compounds.
Dated the 94th dar of
JanuaWAY
D. YOUNG & Co.,
11 & 12 Southampton Buildings, London, W.C.,
Agents for the Applicant.