Improved Process of Treating Certain Descriptions of Auriforous and Argentiforous Material for the Purpose of Facilitating the Separation of the Metals Contained therein.
Year: 1886

page_text: n Improved Process of Treating Certain Descriptions of
Auriforous and Argentiforous Material for the Purpose of
Facilitating the Separation of the Metals Contained therein.
I, ELIZABETH BARNSTON PARNELL, of Sydney, in the Colony of New South
Wales, 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 been designed for the purpose of treating those kinds of
auriferous and argentiferous material which contain sulphur arsenic antimony or
other base metals and its object is to drive off or separate said sulphur and base
metals so as to leave the gold (mixed with such portion of the silver as has not
been converted into a soluble sulphate) "free," and thus facilitate its extraction.
My process is to crush the material to a powder, then to subject it to a low but
gradually increasing heat, and finally to boil it.
I crush the material to a powder in order to increase its surface area and so
allow the heat to reach every part of it more readily and thus reduce the period of
calcination. I heat it gradually so as to drive off the volatile oxides and leave the
metals in the state of soluble sulphates. In practice I find it impossible to effect
these results at one calcination or roasting and so I adopt two. The first takes
say from four to six hours and the heat should not exceed say from 1100 to
1300° Fahrenheit. When this is completed, I draw the charge, and after it is cool
I re-grind it, for it is of great importance to reduce the material to the finest atoms
possible. I then re-calcine or roast it at a much higher heat than before, say from
1200 to 1600° Fahrenheit, sufficient if employed in the first roasting to have run it
into a matt. I continue this roasting until all the volatile oxides have been driven
off and until all the metals which it is possible to make into soluble sulphates have
been reduced to that condition. This effect is usually produced in from five to six
hours.
i
It is almost
. The time occupied in this part of the process may be greatly reduced by·
supplying oxygen (artificially produced) along with the air.
impossible to say how much should be thus supplied because the quantity would
alter with the material under treatment but I have found that with some material
the period of furnacing may be lessened to about one fourth of that stated herein―
that is to say, it may be reduced from periods of eight or twelve hours to periods
of two or three hours.

page_text: The crushed and calcined (or roasted) material I place in a wooden vessel; add
hot water to it and boil for from fifteen to twenty minutes, the object being to
dissolve the soluble sulphates. This, however, is usually not effected at one boiling
but requires two or three. These must be in quick succession so as not to allow
the material to cool and the water must not be allowed to descend below boiling
point. The boiling is complete when a test does not shew the presence of copper.
The crushed dried and boiled material is now ready for any further treatment for
the extraction of its gold which will be in free" condition although it may
possibly be mixed with a small portion of unconverted sulphide of silver. This
"free" gold can be extracted by amalgamation, chlorination, or any other approved
process, my invention terminating when the precious metal is "free." The "soluble
sulphate solution may be conducted into suitable vats and its sulphates preci-
pitated by any of the known processes.
"
The result of the roasting part of my process is to convert the sulphide of iron
into peroxide of iron, and the sulphides of silver, copper, nickel, manganese and
cobalt into soluble sulphates. The galena is converted into sulphate of lead, which
is insoluble, while the arsenic, antimony and a portion of the sulphur volatilizes.
It is very necessary that great care should be exercised in conducting this part of
the process because if the heat be too low, undecomposed sulphides will remain,
and if it be too high, insoluble oxides will be formed instead of soluble sulphates.
I am aware that it is not new to crush auriferous and argentiferous material to
powder and afterwards to calcine it for the purpose of volatilizing the sulphur,
arsenic and antimony. I am also aware that it is not new to boil auriferous
material with quicksilver for the purpose of enlivening the quicksilver-but I am
not aware that such material has ever been calcined to such a degree as to convert
or with the object of converting all or nearly all the metals except the gold into
soluble sulphates neither have I ever heard of such crushed and roasted material
being boiled to such a degree as to convert or with the object of converting said
soluble sulphates into a solution, or of their being boiled in the absence of quick-
silver, the presence of which at this stage would be most injurious to itself.
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. The process as a whole of treating those kinds of auriferous and argentiferous
material (especially pyrites) which contain sulphur, arsenic, antimony or other base
metals substantially as herein described and explained which process consists
essentially in (1st) grinding, (2nd) calcining, and (3rd) boiling such material, the
object of the whole of which is to drive off the volatile oxides, to convert the
sulphides into soluble sulphates, to remove the soluble sulphates in a solution and
to leave the gold and silver "free."
2. The addition of oxygen (artificially produced) to the atmospheric air usually
supplied to auriferous and argentiferous material during the period of roasting or
calcining substantially as herein described and explained.
Dated this thirtieth day of January One thousand sight hundred and nights nive