IMPROVEMENTS IN THE PROCESS OF EXTRACTING SILVER AND GOLD FROM AURIFEROUS AND ARGENTIFEROUS MATTES, ORES OR OTHER PRODUCTS
Year: 1884

page_text: [Communicated from abroad by Pierre Manhès, of 30, Rue du Plat, Lyons,
in the Republic of France, Metallurgist.]
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1 BENJAMIN JOSEPH BARNARD MILLS of the firm of Harris and Mills of
23 Southampton Buildings in the County of Middlesex, Patent Agent do hereby
declare the nature of the said Invention for IMPROVEMENTS IN THE PROCESS OF
EXTRACTING SILVER AND GOLD FROM AURIFEROUS AND ARGENTIFEROUS MATTES,
ORES OR OTHER PRODUCTS and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement:―
The process hereinafter described has for its object the easy and economic
extraction of the gold and silver contained in mattes, ores, and various auriferous or
argentiferous products; it has been specially studied with a view to the extraction
of the gold and of the silver contained in cupreous mattes but it is also applicable
with advantage to the various ores and products containing gold and silver and
particularly to sulphurous complex ores; I therefore claim the exclusive right in.
all its applications.
Beyond the economy, the facility and rapidity of working it presents over all
other processes in use, the advantage of not changing the nature of the materials
from which the precious metals are extracted, which when deprived of these metals,
preserve all their properties and qualities, the cupreous matte for example when
deprived of the gold and silver which it contains remains in the state of matte
(sulphuret of iron and of copper). so that nothing is changed in its ulterior
treatment for copper.
In order that the details of this process may be understood, I will take for
example of the treatment, that of a cupreous, auriferous and argentiferous matte
and this is how I proceed:
The pulverized matte without any previous roasting is mixed as intimately as
possible with a small proportion of sal ammoniac in powder (chlorhydrate of
ammonia) the quantity to be employed of this salt is very small, in general from
one to three per cent of the weight of the matte, but it must be understood that
this quantity necessarily varies according to the proportion of the precious metals
contained in the matte

page_text: The mixture thus prepared is simply heated to a low temperature, until the
disappearance of the ammoniacal vapours which are disengaged in abundance;
I say heated and not roasted because the temperature should be very low as in a
simple heating; it should always remain below red, the matte should remain black,
that is to say that it is necessary that the temperature remain only that required
for the decomposition of the sal-ammoniac without its being sufficiently raised to
decompose the sulphurets of iron and of copper which should remain intact or
nearly so.
The heating can be effected either in a furnace, or in a stove, or in any kind of
receiver and upon any kind of hearth, but in practice I operate by preference in a
closed muffle in order to collect the ammoniacal vapors which are also employed for
the regeneration of the sal-ammoniac by the customary processes.
When the ammoniacal vapours have disappeared, which requires only a short time,
the aspect of the matte has not perceptibly changed in the meantime the gold and
the silver are entirely in the state of chlorides, whilst the iron and the copper have
remained in the state of sulphurets. There remains only to dissolve by one of the
known means the chlorides of gold and of silver and the matte deprived of its
precious metals which it enclosed is afterwards treated in the usual manner for
copper.
I said that the chlorides of gold and of silver formed are dissolved by one of the
known means, but by preference I employ for this dissolution the following
operations which are those which have given the best results.
1. Dissolution of the chlorides in hyposulphite of soda.
2. Precipitation of the metals in the state of sulphurets by an addition of
sulphuret of sodium which regenerates at the same time the hyposulphite liquor.
It is unnecessary to describe here these two operations which are well known
and practised in many works, further they do not constitute my Invention and
I do not claim the right to it, reserving to myself on the contrary the right to
effect the dissolution of the chlorides by any other means which experience would
enable me to recognise as preferable.
My process consists therefore essentially in a new mode of chloridizing the
precious metals and it is characterised by the employment of the chlorhydrate of
ammonia as chloridizing agent joined with a heating to a low temperature not
dcomposing the sulphurets and other compounds in which the gold and the silver
are engaged; it differs completely from the chloridizing processes hitherto employed
not only by that which precedes but also by the suppression of all previous roasting
which renders it more rapid and more economic.
Having now particularly described and ascertained the nature of the said
Invention and in what manner the same is to be performed I declare that what
I claim is the exclusive right of the process of treatment above described for the
extraction of the gold and of the silver contained in mattes, ores or other products
reserving to myself the right to adopt any modifications or improvements which
experience may dictate.
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