IMPROVEMENTS IN MACHINERY POR EFFECTING THE AMALGAMATION OF PRECIOUS METALS
Year: 1858

page_text: PROVISIONAL SPECIFICATION. left by the said 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 "IMPROVEMENTS IN
MACHINERY POR EFFECTING THE AMALGAMATION OF PRECIOUS METALS," (com-
municated to me by a foreigner residing abroad,) to be as follows:-
This machinery for amalgamating gold and silver contained in or with ores
with mercury is constructed as herein-after stated. I take a pan or tub
secured upon a strong frame in such manner as to be capable of being tilted
over, i.e., may rock upon an axis. The sides of the tub may be of wood or
metal, but the bottom should for greater durability be always of metal; this
is put in in the form of a false bottom, so that when worn out it can be easily
and cheaply replaced without disturbing the other parts of the machine. In this
tub there is a revolving muller which is driven round by a shaft; but so as to
allow its weight to rest upon the bottom, and in such manner also as will
permit it to be readily disengaged at the times when the tub is to be tilted to
empty its contents. Two openings for emptying are employed; the first is to
be used to draw off the water and refuse, and the other to empty the amalga-
mated mercury. The first spout is therefore a little above the bottom, while

page_text: the latter is about upon a level with it. The tub is circular, and I prefer to have
it made with the sides flaring; this is set upon a base supported in a strong
frame by a journal or bolt placed at about the middle. While in operation it
is to be kept in a horizontal position, and for this purpose a wedge-shaped
block fits in a space made for the purpose upon the front cross rail of the
frame supporting the tub, a button keeping it in. When the block is in
place the back of the bed rests upon the back cross rail. The false bottom
has an upright post or pin cast upon it at its centre, and which pin entering a
cavity in the muller keeps the latter in a central position in the tub as it
revolves. The spout for drawing off the ground ores after they have been
sufficiently acted upon, and while the tub is maintained in its level position, has
its interior orifice a little above the false bottom, as has already been mentioned.
The spout for pouring off the amalgamated mercury has its orifice very nearly
or quite on a level with the bottom. Into a tub thus constructed is placed a
revolving muller, and this is not to be considered either as an agitator simply
or as a grinding apparatus, but its office is to effect the bringing of all the
particles of solid matter, however finely divided or pulverized previously to
being introduced into the tub, into intimate contact with the quicksilver. A
certain degree of pressure upon the bottom is one of the conditions necessary,
and another is 'the mode in which the materials are agitated, to insure the
passing of all regularly under the bottom of the muller. For effecting this, it
is constructed to act as a partition; dividing the tub into two compartments
from top to bottom or nearly so, or at least to the height at which the ground
ores are admitted. If the muller were of metal of these dimensions (in a full
sized mill) it would be too heavy. I make it therefore of a block of wood; and
face its bottom with iron or other metal. The muller is shaped as a cross bar
with its sides concave, and its ends tapering to the shape of the side of the
tub. The concavity is for the purpose of insuring equality of wear of the
bottom, as by this means the surface is enlarged outward towards the ends
since the rate of wear increases in the proportion of the space passed over.
The muller is made to rotate by a spindle which enters at its lower end into
a cross arm fitting upon two pins-upon the top of the muller, so as to allow of
play and also that the arm may be readily removed, which is done by slipping
it up on the square part of the spindle when the muller is set free. This is
required to be done before tilting the tub. The bottom of the muller may be
also grooved like a millstone.
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From the above it will be seen that the ores containing the precious metals,
and which are to be amalgamated with the mercury, are to be treated by a

page_text: somewhat lengthened operation, and in this it differs from other amalgamators
wherein the mixtures are flowing in and out of the amalgamating' vessels in a
constant stream;. consequently the mercury can act in those only upon such
particles. as are..brought in contact with it, and which contact is effected in
various ways, but always in a transient manner, hence, the great waste; but
by this process a given quantity of materials are only acted upon at a time,
and which action is maintained for the required period to effect the amalga-
mation of the greatest quantity possible out of such given materials, and the
results of which plan have proved successful.
The operation is as follows:-A slow and regular revolution of the muller
is to be maintained by a suitable power. The spouts are to be plugged up.
The pulverized ores containing the precious metals are introduced in a mixture
of water until the tub is nearly full; the mercury being then poured in, the
operation goes on, the quantity of mercury being regulated somewhat by the
richness of the ores. In a full-sized mill, from one to four or five pounds will
be found sufficient. As the muller revolves it constantly passes over the
mercury, spreading it out in a thin stratum upon the bottom, while at the
same time that it sweeps over it also agitates the ores, the lightest spangle of
gold in which will, if brought into contact, be caught by the mercury. The
motion of the muller is such as (while carrying around the whole mass of ores
in the two compartments formed by the said muller) to cause a continual
change of that in one side to that in the other, in order to do which all must
pass beneath in a very thin stratum, and thus be brought into contact with
the mercury. This action is to be maintained for such a period of time as
may be found necessary, requiring generally from one to two hours to exhaust
a charge. It will be seen that this is not a rapid process, but it is certain and
economical. The power required to operate this amalgamator is very moderate
and the attendance necessary very little. In the large way, therefore, a great
train will be kept in operation at once, and these need only be charged and
discharged at regular periods, the attendance of an operator being only
required at those times. At the time for discharging the exhausted ores the
plug in the upper spout is to be removed and the refuse allowed to flow out;
this will be done slowly, the muller still continuing in operation until the
whole has been discharged-as nearly as may be. The amalgamated mercury
will now be exposed and may be examined. If it is still capable of taking up
more gold the tub may be filled up with a fresh supply of ore; if otherwise,
then stop the spindle, lift the driving arm off the pins on the muller, turn the
button, take out the wedge-shaped block, when the tub may be tilted over.

page_text: The plug being then taken out of the lower spout, the mercury is readily
removed. The whole of the mercury by this process is saved, while by the
old a large quantity is lost with the waste ores or in the crevices of the
machines. The tub may now be tilted back and the work continue as
before.