IMPROVEMENTS IN AMALGAMATING AND SEPARATING GOLD AND SILVER FROM QUARTZ AND EARTHS CONTAINING THE SAME, AND IN APPARATUS EMPLOYED THEREIN
Year: 1863

page_text: PROVISIONAL SPECIFICATION left by Richard Archibald Brooman at the
Office of the Commissioners of Patents, with his Petition, on the 9th
October 1863. A communication from Henry Wright Adams and
William Savage Worthington, of New York, United States of America.
I, RICHARD ARCHIBALD BROGMAN, of 166, Fleet Street, in the City of
London, Patent Agent, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN AMALGAMATING AND SEPARATING GOLD AND SILVER FROM QUARTZ
AND EARTHS CONTAINING THE SAME, AND IN APPARATUS EMPLOYED THEREIN," to be
as follows:-
Gold and silver exist in their native state in more or less finely divided
particles in quartz, rock, sand, or earth, either pure or mixed with foreign sub-
stances. The usual method of obtaining these precious metals is to pulverise the
rock or earthy matter containing them when necessary so to do, and mix the
pulverulent dust or sand with liquid quicksilver by stirring or agitation together,
by which the metallic particles are sought to be brought into contact with the
quicksilver, and dissolved by the said liquid metal. The earthy matter is then
separated from the amalgam, and the quicksilver subsequently distilled off*
from the pure metal, but many difficulties have hitherto arisen to prevent the
extraction of all the gold and silver by this method. It is a well-known
chemical law that chemical affinities take place at insensible distances, that is
upon actual contact. To enable the quicksilver therefore to seize and absorb
all the particles of the aforesaid precious metals contained in the metalliferous
dust thus operated upon, it is essential that every separate particle should be

page_text: touched by the said quicksilver. Two hitherto insuperable difficulties have
prevented this indispensible contact. The first is the fact that large portions of
the gold and silver are found mixed and interblended with pyrites, sulphurets,
and many other foreign and baser matters, which effectually coat over the
outer surfaces of these metallic particles, and thus interpose between them
and the quicksilver an obstruction to their amalgamation. The second is the
fact that very large quantities of gold and silver exist in the quartz and metal-
liferous ores and earth in an infinitesimally fine and comminuted state, so
light as to float in the air and run away on the water which is employed in
the various processes of washing and amalgamating. Besides, the difference
of specific gravity is so very great between the liquid quicksilver and this
invisible dust of gold and silver, that it has hitherto been found practically
impossible to amalgamate and save it. The consequence is that not more
than one-half of the above-named precious metals is now obtained by any
known method of amalgamation. The nature and design of this Invention
are to meet and overcome these very serious difficulties. The method of doing
this is to reduce the metalliferous earth ore or quartz to an impalpable powder,
or as nearly so as possible, sift it into a chamber or cylinder, and at the same
time distill into this chamber or cylinder the hot vapor of quicksilver through
an atmosphere of which the said pulverised dust falls or mingles, and the
amalgamation instantly becomes complete. The quicksilver distils at about
-763° Fahrenheit. The vapor of the distilling quicksilver is therefore passed into
the said chamber or cylinder at or near this temperature, while the metal-
liferous dust is sifted into the top of the said reservoir at a lower temperature.
In becoming mixed with the said vapor, the colder pulverized quartz or earth
reduces its temperature, and condenses it in intimate and absolute contact with
every particle of the gold and silver, the hot vapor interpenetrates the foreign
substances that coat over the surfaces of the said metals, absorbs the minutest
particles, and effects a complete amalgamation of all of the precious metals
which the said pulverized quartz, ores, or sand contain. Moreover, the fine dust
of gold and silver which runs away on the top of the water in all processes of
washing is effectually saved. It is confined in an air-tight cylinder or chamber
and mingled in an atmosphere of the distilled vapor of quicksilver in a dry
state, by which its lower temperature causes the said vapor with increased
affinity to condense in contact with each impalpable particle of the gold and
silver, amalgamate instantly with it, increase its specific gravity, and cause it
to subside to the bottom with perfect facility when the mass is agitated with
water for the purpose of washing off the refuse earthy matter.
From many
experiments carefully conducted, it is abundantly demonstrated that surfaces

page_text: of metallic particles so protected by dirt and foreign substances as to prevent
the contact of liquid quicksilver, and consequently hinder amalgamation,
are instantly interpenetrated by the hot vapor, and the said particles thus
enveloped are readily dissolved and amalgamated with the said condensed vapor.
The high heat at which the vapor condenses and seizes the metal increases
the affinity between the two metals. The touch between the vapor and the
precious metal is much closer than between liquid quicksilver and the said
metal, because in the former case contact is complete on all sides, no way of
escape is left. It is enveloped in an impalpable and eliminated state in a hot
atmosphere of the vapor of the distilled quicksilver, which vapor thus in
contact with every metallic particle on all sides at a temperature of 763°
Fahrenheit, or thereabouts, as soon as it touches the said particles of gold and
silver gives up a portion of its caloric to the same, falls below its distilling
temperature, condenses in perfect contact with the metal, amalgamates with it,
and falls down at once by its added gravity. The excess of quicksilver also
condenses like dew in the finest particles. The mass thus operated upon
continuously falls down into a pan or reservoir underneath the chamber or
cylinder, where it is kneaded together with water (hot if possible), then
dissolved by agitation in water, the earthy matter washed off, and the amalgam
and condensed quicksilver obtained by subsidence at the bottom. The process
is continuous and rapid, no vapor escapes, and the quicksilver is all condensed
and used continuously over and over.
The accompanying Drawing shews the apparatus we employ. A is the
cylinder into which the ground quartz is sifted, and through which the said
pulverized metalliferous dust falls in a shower continuously discharged. This
cylinder is eight or ten feet long according to the diameter which may be used.
A cylinder two feet in diameter will be found sufficiently large to work from
10 to 15 tons of quartz per day. The lower end of this cylinder is terminated
in a reduced funnel-shaped point, and extended down near the bottom of the
pan E, from which the amalgamated mass is discharged. Around its lower
end is fitted a cast-iron boot extending up above the water level of the pan,
and terminated at its lower end with a circular plate with scrapers underneath,
setting close down to the bottom of the pan, and rotated by means of the cog
wheels F. The object of this rotating boot and plate is to cause the dis-
charged quartz, amalgam, and fine particles of condensed quicksilver to pass
out between the bottom of the pan and the rotating plate just above it into
the water contained in the pan in a thin and kneaded state, and mixed with
water into a paste or mortar. This rotating plate or boot carries arms or
stirrers for the purpose of agitating and dissolving the said paste in the said

page_text: water, and washing off the earthy matter, and causing the heavier amalgam
and condensed quicksilver to subside to the bottom of the said pan in a recess
formed in the outer perimeter of its bottom. A, stream of water is hept con-
stantly flowing into the said pan, and the agitated and muddy water filled with
the suspended and floating refuse earthy matters is continuously discharged
from a pipe or spout attached to one side of the said pan near its top; B is a
hopper, containing a sieve for the purpose of sifting the ground quartz fed into
the hopper, and discharging it in an equable and continuous shower into the
cylinder A. This hopper rests and turns upon a centre and stationary shaft
running through the centre of the cylinder A, and secured to the bottom of the
pan E. The hopper also sets in a trough J, which surrounds the top of the
cylinder A, which trough contains water for the purpose of sealing this joint.
This hopper and sieve contained within it have a shaking or sifting motion
communicated to them by the arm I, the spring H, and the wheel and pins G.
This latter wheel is ratated by means of the shaft K and the cog wheel F.
When the wheel G moves, the pins attached to it press against the arm I, and
turn the hopper and seive B until the arm I falls off the pin on the wheel G,
when the spring H instantly pulls it back, and causes the. arm I to strike
smartly against the stationary arm or rest L. This alternate motion and sudden
jar of the sieve keep up a continuous sifting action. C is a furnace for heating
the retort D, into which the liquid quicksilver is placed for distillation. The
discharged pipe M leads from the retort D into the cylinder A for the purpose
of conveying the vapor of the distilled quicksilver into the said cylinger. The
quantity of vapor necessary to be thus discharged into the cylinder will depend
upon the size of the cylinder, and the amount of quartz dust sifted into it in a
given time. The only thing to be attended to in this respect is to keep the
cylinder A full of the vapor; when the cylinder is too large to do this with one
discharge pipe from the retort, two or more such pipes may lead from the
retort into the cylinder, or two or more separate retorts and outlet pipes
may be employed for this purpose.