Improvements in Extracting Metals from their Ores or in Obtaining Solutions of same.
Year: 1897

page_text: Date of Application, 8th Feb., 1897
Complete Specification Left, 25th Oct., 1897-Accepted, 27th Nov., 1897
Improvements in Extracting Metals from their Ores or in Obtaining
Solutions of same.
I, FREDERICK WILLIAM STREATFEILD, of 31 Vincent Road, Wood Green, London,
Fellow of the Institute of Chemistry, do hereby declare the nature of this invention
to be as follows:-
This invention relates more particularly to the extraction of gold, silver, and
other metals from their ores, and incidentally to the preparation of a solvent for
such metals.
A description of the treatment to be applied to gold ore will enable any com-
petent chemist to understand the application of the invention to other ores or
metals.
It is a well known fact that gold is not attacked or dissolved by hydrogen
chloride or hydrogen bromide, and it has generally been assumed that acidulated
solutions of the nitrites would act as a reducing agent for such substances as
tri chloride of gold with which they would produce a brown precipitate of
metallic gold.
I have found that when gold or a gold ore is placed in an aqueous solution of
hydrogen chloride or hydrogen bromide together with a salt of nitrous acid,
such as sodium or potassium nitrite, the metal is rapidly attached, and instead
of being thrown down as a precipitate is dissolved and remains in solution from
which it can be precipitated in metallic form by any of the usual methods of
treating such solutions.
For commercial purposes it will generally be preferable to employ hydrochloric
acid in preference to the more expensive hydrobromic acid, and such hydrochloric
acid may be that of ordinary commerce, or it may be generated in situ by the
usual methods. In the same way as the nitrites of sodium and potassium are
now common articles of commerce and have the additional advantage of being
fairly stable compounds and non poisonous, they will probably be generally em-
ployed, but the invention is not restricted to the use of these particular nitrites.
Assume for example it is desired to extract gold from its ore by the use of hydro-
chloric acid and sodium nitrite. In this case the preferably finely powdered ore
which may be previously roasted if necessary is placed in a suitable vessel and
drenched with dilute hydrochloric acid, and to the bath is then added sodium
nitrite in comparatively small successive quantities either in a solid state or in
solution, care being taken to avoid the excessive production of nitrous fumes,
or as an alternative method the ore is drenched with sodium nitrite in solution
and the hydrochloric acid added, but in either case the bath and ore should be
agitated either by the rotation or rocking of the vessel, or by means of suitable
stirrers, if the most rapid and perfect action is to be secured.
The strength of the acid employed may vary within considerable limits, say
from 10 to 30 per cent. of real hydrogen chloride and of such acid about 40 lbs.
will be required for treating 1 cwt. of ore, and the amount of nitrite required

page_text: may likewise vary say from 0.25 to 2.5 per cent. on the ore treated, but no precise
figures can be given, as much will depend upon the class of ore treated, the time
allowed for extraction, and on other circumstances.
Dated the 8th day of February 1897.
Improvements in Extracting Metals from their Ores or in Obtaining
Solutions of same.
I, FREDERICK WILLIAM STREATFEILD of 31 Vincent Road, Wood Green, London,
Fellow of the Institute of Chemistry, do hereby declare the nature of this inven-
tion and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement:
1
This invention relates more particularly to the extraction of gold, silver and
other metals from their ores, and incidentally to the preparation of a solvent for
such metals.
A description of the treatment to be applied to gold ore will enable any com-
petent chemist to understand the application of the invention to other ores or
inėtals.
It is a well known fact that gold is not attacked or dissolved by hydrogen
chloride or hydrogen bromide, and it has generally been assumed that acidulated
solutions of the nitrites would act as a reducing agent for such substances, as
tri-chloride of gold, with which they would produce a brown precipitate of
metallic gold.
I have found that when gold, or a gold ore, is placed in an aqueous solution of
hydrogen chloride or hydrogen bromide, together with a salt of nitrous acid, such
as sodium or potassium nitrite, the metal is rapidly attacked, and instead of being
thrown down as a precipitate, is dissolved, and remains in solution, from which
it can be precipitated in metallic form by any of the usual methods of treating such
solutions.
For commercial purposes it will generally be preferable to employ hydrochloric
acid in preference to the more expensive hydrobromic acid, and such hydro-
chloric acid may be that of ordinary commerce, or it may be generated in situ
by the usual methods. In the same way as the nitrites of sodium and
potassium are now common articles of commerce, and have the additional advan-
tage of being fairly stable compounds and non-poisonous, they will probably
be generaly employed, but the invention is not restricted to the use of these
particular nitrites."
Assume, for example it is desired to extract gold from its ore by the use of
Hydrochloric acid and sodium nitrite. In this case the preferably finely pow-
dered are which may he previously roasted if necessary, is placed in a suitable
vessel, and drenched with dilute hydrochloric acid, and to the bath is then added
sodium nitrite in comparatively small successive quantities, either in a solid state
or in solution, care being taken to avoid the excessive production of nitrous
fumes, or as an alternative method the ore is drenched with sodium nitrite in
solution and the hydrochloric acid added, but in either case the bath and ore
should be agitated either by the rotation or rocking of the vessel, or by means of
suitable stirrers, if the most rapid and perfect action is to be secured.

page_text: The strength of the acid employed may vary within considerable limits, say
from 10 to 30 per cent. of real hydrogen chloride and of such acid about 40 lbs.
will be required for treating 1 ewt of ore, and the amount of nitrite required may
likewise vary say from 025 to 25 per cent, on the ore treated, but no precise
figures can be given, as much will depend upon the class of ore treated, the time
allowed for extraction, and on other circumstances.
Having now particularly described and ascertained the nature of my said in-
vention and in what manner the same is to be performed, I declare that what
I claim is:-
1. The improvements in extracting metals from their ores, or in obtaining
solutions of same, consisting in submitting such metal or ore to the action of
hydrogen chloride or hydrogen bromide and a salt of. nitrous acid, substantially
as described.
2. The improvements in extracting metals from their ores, or in obtaining
solutions of same, consisting in submitting such metal or ore to the action of
dilute hydrochloric acid and a salt of nitrous acid, substantially as described.
Dated this 99.1 of
100
For the Applicant,
PHILIP M. JUSTICE,
55 and 56 Chancery Lane, London, Chartered Patent Agent.