Improvements in Extracting Gold and Silver from Ores or other Compounds.
Year: 1888

page_text: Date of Application, 14th July, 1888
Complete Specification Left, 21st Feb., 1889-Accepted, 18th July, 1889
DI MUITIVATION.
Improvements in Extracting Gold and Silver from Ores or other
Compounds.
We, JOHN STEWART MAC ARTHUR, Analytical and Technical Chemist, of 15 Princes
Street, Pollokshields, in the County of Renfrew, ROBERT WARDROP FORREST, M.D.
and WILLIAM FORREST, M.B., both of 319 Crown Street, Glasgow, in the County of
Lanark, do hereby declare the nature of this invention to be as follows:-
Our said Invention. relates principally to processes of the kind described in our
Patent Specification No. 14174 of 1887, and has for its objects to improve the same,
and also to lessen the quantities of chemicals employed therein..
One improvement consists in preparatorily treating or mixing the powdered ore or
other compound with potash, or lime, or other alkali or alkaline earth, which may be
allowed to remain with the ore or compound, or which may be washed out if soluble.
In some cases, as for example when mercury cyanide is used, it is advantageous for
the alkali or alkaline earth to remain.
After this preparatory treatment the ore, or compound, which may consist of
tailings or residues from other processes or operations, may be treated as described in
our earlier Specification herein before referred to; we prefer however to cause the
cyanide solution to percolate through the materials once or oftener until all or nearly
all the precious metals are dissolved. For this percolation very simple tanks, vats, or
vessels may be used, such vessels being provided with permeable false bottoms or any
suitable filtering apparatus.
The separated solution is next made to pass through a mass of metallic zinc in a
state of fine division. We find that the best results are obtained in this part of the
process when the zine has been freshly divided by mechanical or other means so that .
its surfaces are as purely metallic as possible; and further when the quantity or mass
of zinc employed is such that the solution has in passing through it ample opportunity
for being thoroughly acted on.
This improved zinc process is also advantageously applicable with other than
cyanide solutions containing the precious metals, that is with solutions, such, for
instance, as chlorides, thiosulphates (sometimes called hyposulphites) or sulphates,"
obtained in the well known Plattner, Von Patera, Russell, and Augustine extracting
processes.
The precious metals may be separated from any excess of zinc, after separation of
the solution, by distillation. Or the larger portion of the precious metals may be
separated from excess of zinc by sieving, (by preference under water) when with a
suitable sieve the greater part of the precious metals will pass through, the greater
part of the zine being left on the sieve.'
Improvements in Extracting Gold and Silver from Ores or other
Compounds.
We, JOHN STEWART MAC ARTHUR, Analytical and Technical Chemist, of 15 Princes
Street, Pollokshields, in the County of Renfrew, North Britain, ROBERT WARDROP
FORREST, M.D., and WILLIAM FORREST, M.B., both of 319 Crown Street, Glasgow,