Improvements in Concentrating and Separating Certain Metals from their Ores.
Year: 1899

page_text: Date of Application, 7th Feb., 1899
Complete Specification Left, 7th Nov., 1899-Accepted, 13th Jan., 1900
Improvements in Concentrating and Separating Certain Metals from
their Ores.
I, WILLIAM ALLISON MACFADYEN, of Pretoria, in the South African Republic,
Advocate, do hereby declare the nature of my invention to be as follows;
This invention relates to an improved means of concentrating and separating
from their ores the following metals:-bismuth, gold, silver, copper, lead, zinc,
tin and mercury, by taking advantage of their diamagnetic properties, and, also,
as the diamagnetic effect is small, by providing a means of increasing it.
After the ore has been crushed to a proper fineness, and dried in a suitable
manner, it is passed in a stream of particles down a fall or chute. As it falls
it is submitted to the action of a magnet, or series of magnets, which divert
all the paramagnetic elements into a shunt, receptacle, or opening to one side
of the stream. The object of this part of the process is
(1) To clear the pulverised ore of all paramagnetic substances which might
adhere to the magnets used in the subsequent process, and thus block the passage
of the particles as they pass the separators, and
(2) To secure, for further treatment, such metallic particles as may be com-
pounded with magnetic elements, and thus are not amenable to diamagnetic
separation.
The pulverised ore is then passed through another series of falls or chutes, in
the course of which it is submitted to the action of a strong magnetic field or
fields. In passing through these, the metallic particles experience a repelling
force which tends to drive them away from the pole of the magnet, or, if the
field is between the poles, they are repelled equatorially, 1.e. they tend in a
direction, perpendicular to the line joining these poles. These chutes include
both perpendicular and oblique arrangements of the passage, with an opening
or openings, in the direction of the repulsion, and also helical or vermiform
arrangements in order to concentrate the metallic particles in the centre of the
stream as it falls
After passing through the chutes the stream should discharge upon the outer
rim of the circular end of the core of a strongly excited electromagnet. As the
force is much stronger at the edges than in the centre, the metallic particles will
leave the edges and collect in the centre, where they can be taken up by a
suitable scoop or gatherer, or pass down through an opening in the centre of
the magnet, while the tailings are swept off down the outer sides. In order to
facilitate this process the electromagnet may be made to revolve, and in order
to relieve the friction of the particles, and render their movement of translation
easier, an up-and-down vibration should be imparted to the electromagnet. The
face of the core of the electromagnet may be sloped or grooved in order to help
the translative movement, as may be found desirable.
as
The diamagnetic effect, however, is with ordinary electromagnets so small':
to be difficult to use. To make it capable of being used in dealing with ores
as a commercial process, it must be increased. One way of doing this is by

page_text: increasing the strength of the electromagnet. The increase of the effect by this
means, however, is limited by the point of saturation of the iron of the electro-
magnet core.
I propose, therefore, to increase it also in another way. The diamagnetic effect
is not absolute and unchangeable. It is relative. The resultant magnetic action
of any body or particle is the difference between the action on the movable body
and the surrounding medium-that is what it would have been on the portion
of the medium which the movable body displaces Thus if the air can be
rendered more permeable to magnetism, as the air remains unmoved, the resultant
translative action upon the metals will be increased
This I propose to do by exposing the magnetic field, or fields, through which
the pulverised ore passes, whether in the chutes, or on the circular core of the
electromagnet, to a radiation, one of whose properties is to make the air through
which it passes a good conductor of electricity Such a radiation is emitted by
salts of uranium, thorium and its compounds, and polonium and its compounds.
The radiation should be arranged, as much as possible, so as to have its centre
near the point of greatest magnetic force.
Thus the metallic particles, passing through the magnetic field and the super-
imposed field of radiation, exhibit a movement of deflection and translation, which
is sufficiently large to be taken advantage of for purposes of separation in the
beforementioned manner.
The electromagnets used should be strong.
Provision may be made for reduplicating the process by passing the tailings,
through shunts or switches, back to the beginning of the process, in order to
run the gauntlet again.
Dated at Ductavia the 16th law of January 1900
Improvements in Concentrating and Separating certain Metals from
their Ores.
I, WILLIAM ALLISON MACFADYEN, of Pretoria, in the South African Republic,
Advocate, do hereby declare the nature of this invention, and in what manner
the same is to be performed, to be particularly described and ascertained m and
by the following statement:-
This process is an improved means of concentrating and separating from
their ores certain diamagnetic metals, by taking advantage of their property
of diamagnetic repulsion, tending from the stronger to the weaker parts of a
magnetic field; and also as the diamagnetic effect is small by providing a means
of increasing it, consisting of placing a substance within the magnetic field
emitting a radiation which renders the air through which the particles pass a
good conductor of electricity. I propose to deal in this way with gold, but the
method is also applicable to other diamagnetic metals such as bismuth, silver,
copper, lead, zinc, tin and mercury and their diamagnetic compounds.
In carrying out my invention the ore must first be crushed to a proper fineness,
which may be done by any system of either wet or dry crushing. I prefer that
it should be dry-crushed, but provided the requisite degree of fineness is attained

page_text: either process may be employed. The requisite degree of fineness varies with
the ore to be treated, but I find in practice that a sieve having 500 meshes per
square inch for the first treatment of gold ores gives sufficient fineness.
The crushed particles are dried, in any known way provided that the matter
is thoroughly pulverised and completely friable. Action on oies containing
oxides is facilitated by submitting the particles in the drying process to a
moderate roasting, but generally this is not essential
After the ore has been crushed to a proper fineness and suitably dried, the
particles are passed in a stream through ordinary magnetic separators, in order
to clear the ore of all paramagnetic substances, such as iron, cobalt, nickel, etc.,
which might adhere to the magnets used in the subsequent process and block
passage through the diamagnetic separators. The paramagnetic substances thus
withdrawn may be afterwards treated as described.
The pulverised ore, freed from paramagnetic substances, is passed through
another series of chutes, in the course of which it is submitted to the action of
strong magnetic fields In passing these the metallic particles experience a
repelling force from the stronger to the weaker parts of the magnetic field. This
field may be applied to divert particles sideways from an oblique, descending
stream, or it may be made to act in other directions. If the powder is placed
upon the horizontal core of an excited electro-magnet, the diamagnetic particles
collect in the centre, if aided by vibration.
The diamagnetic effect of diverting particles is however, extremely small in
itself. To render it practically useful it must be increased. As the increase of
the power of an electiomagnet is limited by the point of saturation of the iron
of its core, I have recourse to another device.
The magnetic action on any body or particle is the difference between that
which it would have upon the movable body itself and that which it would
have on that portion of the surrounding medium which the movable body dis-
places. Thus, if the air can be rendered more susceptible, the diverting action
upon the particles would be increased. I attain this by exposing the air within
the magnetic field to a radiation which renders the air exposed to it a good
conductor of electricity. For this purpose I place salts of uranium, thorium,
pollonium, radium or their compounds (see Chemical News, 1898, Vol. 78,
page 49, and 1899, Vol. 79, page 1), in a Geissler or other similar vacuum tube
and apply a high tension current of electricity. Other arrangements are, how-
ever, possible, as the radiation is inherent in the substances. In practice the best
results are obtained by using pollonium or radium
By means of the radio-activity arising from these salts employed in con-
junction with a strong electromagnet, I obtain a diversion of the diamagnetic
particles, sufficient for practical use in separating them from the rest, and thus
I can effect cheaply a concentration of the diamagnetic particles which can be
enhanced by repetition.
My invention may be more readily understood by reference to the accom-
panying drawings, which illustrate apparatus for effecting the diamagnetic
separation.
Fig. 1 is a vertical section of apparatus consisting of a chute with a side
opening for the diverted particles opposite an electromagnet having two poles
operating and a radio-active tube between the poles.
Fig is a vertical section of similar apparatus having an electromagnet, with
one pole operating, and a radio-active tube on one side of the pole.
Fig. 3 is a front view of a similar apparatus having the poles of an electro-
magnet at each side and a radio-active tube between them.
Fig 4 is a plan of the same
The same letters refer to like parts in each figure.
a is a chute: an electromagnet, e a Geissler or like tube containing a radio-
active substance, such as salts of uranium, thorium, pollonium, or radium, excited
by a disruptive discharge, d represents the descending particles; e the particles

page_text: concentrated and f are the tailings, g being the opening for diversion of the
.separated metal.
The crushed particles descend the chute a and when opposite the electro-
magnets 6 and within the sphere of the radio-activity of the tube c the metal
to be separated experiences a repulsion sufficient to drive it through the open-
ing whilst the tailings f pass to the dump. The particles e are concentrates.
Obviously other arrangements may be employed which superimpose the field
of radiation on the magnetic field.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:
1. The herein described process for concentrating metallic particles, by pass-
ing dry finely crushed ore repeatedly if necessary through a strong magnetic
field, upon which is superimposed a radiation rendering the air within its field
a good conductor of electricity, whereby the diamagnetic particles being repelled
from the stronger to the weaker parts of the field are diverted from the stream
and collected as concentrates.
2. The combined process for concentrating metallic particles, which consists
of the following steps of operation: First separating paramagnetic particles
by passing the dry finely crushed ore through a magnetic separating apparatus.
and, secondly, passing the ore from which the paramagnetic particles have been
separated through a strong magnetic field, repeatedly if necessary, upon which
is superimposed a radiation, one of whose properties is to render the air within
its field a good conductor of electricity, whereby the diamagnetic particles, being
repelled from the stronger to the weaker parts of the field, are diverted from the
stream and collected as concentrates, substantially as described.
Dated this 7th day of November 1899.
ABEL & IMRAY,
Agents for the Applicant.