Improvements in Gold and Silver Extraction.
Year: 1898

page_text: Date of Application, 27th July, 1898
Complete Specification Left, 26th Apr., 1899-Accepted, 24th June, 1899
Improvements in Gold and Silver Extraction.
I, JOHN JAMES Hood, of 1, Fenchurch Avenue, in the City of London, Chemist,
do hereby declare the nature of this invention to be as follows: -
These improvements relate to the precipitation or extraction of gold from its
solutions, more particularly from such solutions as are obtained in the various
wet or lixiviation processes practised for the extraction of gold from its ores.
The solution contaming the gold may be either slightly alkaline, or slightly
acid, and it may be percolated through the precipitating material contained in
boxes or similar apparatus constructed of wood or other suitable material, or the pre-
cipitating material may be contained in the form of cakes produced in a filter press
through which the gold solution may be forced or by other suitable contrivance.
The material I employ is more particularly suitable for dealing with the gold
solutions obtained when employing the mercury solvent described and patented
by me (English Patent No. 14155 of 1894). When that solvent is employed the
solutions invariably contain an excess of mercury together with the gold and
silver, and the object is to recover such excess of mercury as well as the gold and
silver contained in the solution. The proportion of ingredients I employ in
making the precipitant may be varied, but that which I find to give satisfactory
results and the method of making the incorporation are as follows:-100 parts of
zine are melted in an ordinary iron or clay pot to which is added a quantity of
metallic antimony equal to 5 parts previously melted in a separate pot. The mix-
ture is thoroughly stirred and allowed to cool until it begins to solidify, there
is then added 20 parts of metallic mercury, previously heated to nearly boiling,
and the whole mixture is thoroughly stirred and poured into slabs or moulds of
convenient shape. In this form the zinc-antimony couple is suitable for trans-
port. When the precipitant is required for use it is melted at the lowest possible
temperature and granulated by pouring the melted material in a thin stream into
water. The granulated alloy may then be broken up with the greatest case to
any degree of fineness necessary for the precipitation of gold.
Instead of employing antimony with the zinc and mercury, I may use bismuth,
arsenic, or phosphorus. In making the arsenic or phosphorus precipitant I prefer
to first make a compound of lead and arsenic, or phosphorus, and add such body
to the molten zinc and subsequently the mercury as already described. These
alloys when granulated may be broken up to any degree of fineness with case,
and in this form are employed for charging the precipitating boxes or filter
presses. Such a zinc-antimony alloy acting as a galvanic couple forms a very
active precipitant for gold as well as for mercury. When employed in conjunc-
tion with the mercury solvent for gold already referred to, the precipitant is
worked until it is well charged with mercury resulting from the excess of the
solvent used in leaching the ores. The material is taken out of its receptacle,
dried, and subjected to distillation, and afterwards replaced for use until it is.

page_text: sufficiently charged with gold, when, after the final distillation to obtain the
mercury, it is treated by any of the ordinary methods for recovery of the precious
metals.
CARPMAEL & Co.,
Agents for the Applicant.
I, JOHN JAMES HOOD, of 1, Fenchurch Avenue, in the City of London, Chemist,
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 follow-
ing statement:-
These improvements relate to the precipitation or extraction of gold from its
solutions, more particularly from such solutions as are obtained in the various
wet or lixiviation processes practised for the extraction of gold from its ores.
The solution containing the gold may be either slightly alkaline, or slightly
acid, and it may be percolated through the precipitating material contained in
boxes or similar apparatus constructed of wood or other suitable material, or the pre-
cipitating material may be contained in the form of cakes produced in a filter press
through which the gold solution may be forced or by other suitable contrivance.
The material I employ is more particularly suitable for dealing with the gold
solutions obtained when employing the mercury solvent described and patented
by me (English Patent No. 14155 of 1894). When that solvent is employed the
solutions invariably contain an excess of mercury together with the gold and
silver, and the object is to recover such excess of mercury as well as the gold and
silver contained in the solution. The proportion of ingredients I employ in
making the precipitant may be varied, but that which I find to give satisfactory
results and the method of making the incorporation are as follows;-100 parts of
zinc are melted in an ordinary iron or clay pot to which is added a quantity of
metallic antimony equal to 5 parts previously melted in a separate pot. The mix-
ture is thoroughly stirred and allowed to cool until it begins to solidify, there
is then added 20 parts of metallic mercury, previously heated to nearly boiling,
and the whole mixture is thoroughly stirred and poured into slabs or moulds of
convenient shape. In this form the zinc-antimony couple is suitable for trans-
port. When the precipitant is required for use it is melted at the lowest possible
temperature and granulated by pouring the melted material in a thin stream into
water. The granulated alloy may then be broken up with the greatest case to
any degree of fineness necessary for the precipitation of gold.
Instead of employing antimony with the zinc and mercury, I may use bismuth,
arsenic, or phosphorus. In making the arsenic or phosphorus precipitant I prefer
to first make a compound of lead and arsenic, or phosphorus, and add such body
to the molten zinc and subsequently the mercury as already described. These
alloys when granulated may be broken up to any degree of fineness with case,
and in this form are employed for charging the precipitating boxes or filter
presses. Such a zinc-antimony alloy acting as a galvanic couple forms a very
active precipitant for gold as well as for mercury. When employed in conjunc-
tion with the mercury solvent for gold already referred to, the precipitant is
worked until it is well charged with mercury resulting from the excess of the
solvent used in leaching the ores. The material is taken out of its receptacle,
dried, and subjected to distillation, and afterwards replaced for use until it is

page_text: sufficiently charged with gold, when, after the final distillation to obtain the
mercury, it is treated by any of the ordinary methods for recovery of the precious
metals.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:
1. A precipitant consisting of an alloy of zinc, antimony (or bismuth, arsenic
or phosphorus) and mercury in about the proportions specified.
2. The process of manufacturing a precipitant consisting in melting and mix-
ing zinc and antimony, allowing the mixture to cool until it begins to solidify,
and then adding mercury heated nearly to boiling.
3. Extracting gold and silver from solutions, by bringing the solutions into
contact with an alloy of zinc, antimony and mercury.
4. Extracting gold, silver and mercury from solutions, by bringing the solu-
tions into contact with an alloy of zinc, antimony and mercury, from time to time
distilling off mercury from the alloy, and finally recovering the gold and silver
from it.
5. The method of extracting gold and silver substantially as described.