AN IMPROVED PROCESS FOR EXTRACTING GOLD FROM AURIFEROUS PYRITES AND OTHER ORES OR REGULUS CONTAINING GOLD "
Year: 1883

page_text: LETTERS PATENT to Thomas Bowen and James Napier both of Swansea in
the County of Glamorgan both Chemists for an Invention of "AN IMPROVED
PROCESS FOR EXTRACTING GOLD FROM AURIFEROUS PYRITES AND OTHER ORES
OR REGULUS CONTAINING GOLD
"
PROVISIONAL SPECIFICATION left by the said Thomas Bowen and James
Napier at the Office of the Commissioners of Patents on the 26th April
1883.
THOMAS BOWEN and JAMES NAPIER both of Swansea in the County of
Glamorgan both Chemists
"
AN IMPROVED PROCESS FOR EXTRACTING GOLD FROM
AURIFEROUS PYRITES AND OTHER ORES OR REGULUS CONTAINING GOLD
"
This invention has for its object an improved process for extracting gold
from auriferous pyrites and other ores or regulus containing gold and the process
is applicable when the ore or regulus does not contain more than six per cent of
copper.
The ore having been calcined by any well known method, until the remaining
sulphur does not exceed five or six per cent is thoroughly mixed with about ten
per cent of its own weight of common salt and then heated for some hours in
calciners, constructed in any ordinary form (preferably in muffled calciners) which
if it be intended, as would be desirable on the score of economy, to collect the
hydrochloric acid gas produced, should be placed in connection with condensing
towers constructed in the ordinary way filled with coke or any equivalent material,
through which a current of water slowly percolates.-These towers will condense
the acid fumes produced in salting, and also any gold or silver volatilized during
the process. In calcining the ore with salt it is desirable that the mixed ore and
salt should be stirred from time to time and that the temperature should not be
raised above a dull red heat A sample, drawn from time to time will serve to
indicate whether the calcination has proceeded far enough, so that the next stage of
the process may be commenced.-For this purpose the sample should be heated
with concentrated pure nitric acid, when the evolution of nitrous acid fumes will
Price 211

page_text: indicate that the calcination is not completely effected-when on the other hand
the sample, thus treated, gives off no fames of nitrous acid gas, the process of
calcination may be considered complete.
The operation of salting having been thus completed, the ore is drawn from the
calciners on to a floor where it is allowed to get cold, it is then thoroughly mixed
with about two per cent of chloride of lime (ordinary bleaching powder will do)
in powder or the ore may be moistened with a solution of it-this solution to
be of adequate strength should be made and applied in about the following
proportions To three cubic feet of the calcined ore one cubic foot of water
containing chloride of lime in the proportion of two per cent by weight to the
weight of this ore should be added this will saturate the ore, and convert the
mixture into the consistency of paste.-In place of chloride of lime any other
compound of chlorine might be used which is capable of yielding its chlorine to
the ore, when decomposed by an acid solution as hereinafter described, or in any
other appropriate manner.-In like manner and to effect the same purpose, about
five per cent of manganese peroxide may be employed, with a solution of hydro-
chloric acid applied in the way to be presently described, the essential matter
being, that chlorine should be brought to re-act intimately upon every particle of
gold contained in the calcined ore.
(
The ore having been thus treated is placed in tanks provided with perforated
false bottoms, which are covered with coarse sacking or other light material to
act as a filter, In these tanks the ore is treated with an acid solution in the
following manner
The tank is provided with a wooden or lead tube, which passes from the top of
the tank through the ore contained in the tank and through the false bottom, down
to the bottom of the tank. The tank is also provided with a tap at the bottom
of it
An acid solution is then made with hot water, and either hydrochloric, or
sulphuric or any other acid, strong enough to decompose the chloride of lime and
liberate the chlorine therein contained.-The tap which issues from the bottom of
the tank having been closed, and the tank being filled with the ore resting on the
false bottom, the hot acid solution is poured gradually down the pipe and rises
gradually up through the mixed ore and chloride of lime, liberating the chlorine
on its way which takes up the gold from the ore as it comes into intimate contact
with it,
It is desirable to allow the ore to soak for an hour or two in this hot acid
solution before the tap is opened. At the end of this time, the tap is opened and
the solution allowed to run out into the precipitating vessels (which may be of any
convenient size and shape) hot water being gradually poured, not down the pipe,
but on to the top of the ore as it lies in the tank, at the same rate as the liquor
escapes at the bottom-this should be continued until a sample drawn from the
tap gives no indication of gold when tested with protochloride of tin.
The gold is then precipitated from this solution in which it has been rendered
soluble, as metallic gold by any of the well known means, such for example as by
copper precipitate.-ferrous sulphate, or oxalic acid
The precipated gold, after being carefully dried may be fused direct, or it may
be freed from any impurity by refining with metallic lead, and recovered by the
cupel. In case the ore should contain a small quantity of silver it will be found
to have been washed out with the gold and may be precipitated by well known
means.