AN IMPROVEMENT IN TREATING ORES OF PRECIOUS METALS
Year: 1858

page_text: PROVISIONAL SPECIFICATION' left by Richard Archibald Brooman at the
Office of the Commissioners of Patents, with his Petition, on the 22nd
February 1858.-A communication.
I, RICHARD ARCHIBALD BROOMAN, of 166, Fleet Street, in the City of
London, E.C, Editor of the Mechanics' Magazine and Patent Agent, do
hereby declare the nature of the said Invention for "AN IMPROVEMENT IN
TREATING ORES OF PRECIOUS METALS," (communicated to me by a foreigner
residing abroad,) to be as follows:-
This Invention is for an improvement in treating ores of the precious metals.
preparatory to amalgamation, and its object is to economise the operation by:
préventing loss of 'quicksilver, as well as to secure a large product of gold and
silver. This discovery is more particularly designed for treating auro-pyritous
ores (and the tailings" left from such as may have been operated upon in
the old way), and the principle of the said Invention lies chiefly in submitting.
such auro-pyritous ores to a treatment of pyroligneous, acetic, or other similar
vegetable acid, which treatment produces certain effects upon the sulphurets of
gold, whereby the metallic gold being liberated may thus be easily amalga-
mated with quicksilver. This treatment has also the effect of neutralizing, or
counteracting, or correcting the alkaline nature of certain gangues which act
to impede the amalgamating process, and to render it slow and defective.
It is well known that by the old way of roasting such ores, or in their
treatment with mineral acids and salts, there is a loss to a very serious extent,
in the one case by volatilization, and in the other by destroying the quicksilver,

page_text: and this effect is also produced by all ores of a pyritous nature when submitted
without previous chemical treatment to be amalgamated.
The Inventor states he has discovered that the employment of pyro-
ligneous, acetic, or other like vegetable acids, in the treatment of the ores above
described, has resulted in a large saving of the mercury, and also in the
increased product of gold, so much so indeed that he is enabled to operate
very profitably upon "tailings" held to be too poor to pay for the working by
any of the old modes.
The ores are first to be reduced by grinding, in any of the usual methods to
as minute a subdivision as may be, the finer the better; I then put a charge
of the said ores into a boiler or cauldron of suitable size, according to the
quantity to be operated upon. The vegetable acid is then introduced, if
pyroligneous acid, of the usual commercial strength, say, to every bushel of the
ground ores one gallon or thereabouts of acid. The temperature is then to
be raised to the boiling point, and so continued from four to six hours, and
until the whole of. the acid is. evaporated. The ores may now be operated
upon with quicksilver, in the usual way, or, as I prefer, by means of a new
amalgamating mill, a Provisional Specification of which I have filed in the
Patent Office as a separate application for Letters Patent, of even date
herewith.
If acetic, oxalic, or other vegetable acid is to be used instead of pyroligneous,
(which latter, from its cheapness and the readiness with which it may be
manufactured at the mines, will be likely to be most employed), its strength
may be regulated by the addition of water, or it may be poured into the boiler
where the ores have already been mixed with water, and then subjected to
heat and evaporation as before.
Heat is not absolutely necessary, its use being to hasten the process. The
acid may be employed to the ground ore, and allowed to act upon it for several
months under the ordinary temperature of the atmosphere, and then those may
be submitted to the amalgamating process.