A Process for Precipitating Gold and other Precious Metals from Solutions Used for Extracting such Metals from their Ores.
Year: 1895

page_text: Date of Application, 13th July, 1895
Complete Specification Left, 13th Apr., 1896-Accepted, 23rd May, 1896
PROVISIONAL SPECIFICATION.
A Process for Precipitating Gold and other Precious Metals from
Solutions Used for Extracting such Metals from their Ores.
I, MIDDLETON CRAWFORD, of Colorado Springs, in the State of Colorado,
U.S.A., Mining Engineer, do hereby declare the nature of this invention to be as
follows:-
This invention has for its object a process for precipitating gold and other
precious metals from solutions used for extracting such metals from their ores.
At the present time weak solutions of potassium cyanide and the like are
largely used in treating the ores of gold and other precious metals, and afterwards
zinc shavings are commonly used to precipitate the precious metal out of
solution; a better means for precipitating the precious metal is however much
needed.
I employ suitably prepared charcoal filters: I granulate the charcoal to about
the size of shot, separating all dust therefrom. I saturate the granules with
a solution, it may be of sulphate of alumina, or sulphate of iron or sulphate of
copper, or sulphate of zinc.
For gold, the sulphate of alumina is the most suitable and for silver, the
sulphate of iron; if both metals be present in the ore these sulphates may be used
either together or in successive filters. In all cases I render the sulphate neutral,
and this I do preferably by adding silicate of soda. The saturated charcoal
is dried and heated to redness; when cool it is ready to take its place in the
filter.
The liquor on being passed through the filter deposits the precious metal
amongst the charcoal; the liquor is otherwise unaffected, no waste of cyanide
ensues. It is preferred to employ two or more filters in series. When the filter
bed has become sufficiently rich, the metal is smelted out.
Dated this 19th day of Jule 1895
A Process for Precipitating Gold and other Precious Metals from
Solutions Used for Extracting such Metals from their Ores.
I, MIDDLETON CRAWFORD, of Colorado Springs, in the State of Colorado,
U.S.A., Mining Engineer, 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 :-
This invention has for its object a process for precipitating gold and other
precious metals from solutions used for extracting such metals from their ores.
At the present time weak solutions of chlorine, potassium cyanide and other
solvents are largely used in treating the ores of gold and other precious metals,
and afterwards zinc shavings.are commonly used to precipitate the precious metal
out of solution; a better means for precipitating the precious metal is however
much needed.

page_text: I employ suitably prepared charcoal filters; I granulate the charcoal to about
the size of shot, separating all dust therefrom. I saturate the granules with a
solution (preferably nearly saturated) of sulphate of alumina, or sulphate of iron,
or sulphate of copper, or sulphate of zinc.
Preferably I use two or more layers of the filtering material, the size increasing
from the upper layer downwards. Thus a suitable arrangement is to have three
layers each about 2 inches in thickness the granules of the upper layer being
about th of an inch in diameter, of the middle layer about th and of the lower
layer th.
For gold, the sulphate of alumina is the most suitable and for silver, the
sulphate of iron; if both metals be present in the ore these sulphates may be
used either together or in successive filters. In all cases I render the sulphate
neutral, and this I do preferably by adding silicate of soda. The saturated
charcoal is dried and heated to redness; when cool it is ready to take its place in
the filter.
The liquor on being passed through the filter deposits the precious metal
amongst the charcoal; the liquor is otherwise unaffected, no waste of cyanide
ensues. It is preferred to employ two or more filters in series. When the filter bed
has become sufficiently rich, the metal is smelted out.
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. Precipitating gold and other precious metals from solutions by filtration
through charcoal chemically prepared with alumina, iron, copper or zinc as above
set forth.
2. Precipitating gold from solutions by filtration through charcoal prepared
with sulphate of alumina and subjected to heat.
3. Precipitating silver from solutions by filtration through charcoal prepared
with sulphate of iron and subjected to heat.
Dated this 11th day of April 1896.
M. CRAWFORD.