Improvements in the Method of and Apparatus for Effecting the Separation of Iron or Iron Ores by Mechanical Means from Associated Gangue.
Year: 1888

page_text: Date of Application, 3rd Dec., 1888
Complete Specification Left, 2nd Sept., 1889-Accepted, 12th Oct., 1889
PROVISIONAL SPECIFICATION.
Improvements in the Method of and Apparatus for Effecting the
Separation of Iron or Iron Ores by Mechanical Means from
Associated Gangue.
I, BENJAMIN JOSEPH BARNARD MILLS of 23 Southampton Buildings, in the County
of Middlesex, Patent Agent, do hereby declare the nature of this invention, a com-
munication to me from abroad by Thomas Alva Edison of Llewellyn Park, in the
County of Essex, and State of New Jersey, United States of America, Inventor, to
be as follows:-
This invention relates to that character of iron ores known as oolithic ores, the
object of the invention being to effectively separate the iron of such ores from the
material which surrounds the same. The iron of these ores is non-magnetic iron, and
it has been attempted to reduce it to a magnetic condition, so that it can be operated
upon by a magnetic separator by heating the same and then cooling it; but since
in these ores the iron is in the form of small plates, or tablets surrounded by earthy
matter, it is found that when they are heated, such earthy matter hardens and cakes
on the iron tablets, so that the separation cannot be perfectly accomplished by the
magnet. It is therefore necessary to employ mechanical means for separating the
metal from the earthy material, and this inventor has devised a method and apparatus
for doing this, which constitutes the present invention.
In carrying the invention into effect, the ore is first crushed between rollers
sufficiently to separate the tablets from one another, and it then passes from the
rollers into a hopper, from which it is allowed to escape, a portion at a time, into a
turning cylinder, in which are placed large pieces of hard material, such as quartz or
emery, the pieces being of from 10 to 15 pounds weight. This cylinder is
revolved for a time and, by the friction of the particles within it upon
each other and upon the pieces of hard material, the earthy covering is
removed from the tablets. The whole mass contained in the turning cylinder,
except the large pieces of hard material, is then placed in a revolving inclined
cylindrical screen, by which the fine particles of earthy matter are separated from the
iron tablets. The tablets of oolithic iron are very nearly of the same size, and in
those from one mine, for instance, practically the whole of the tablets will pass
through a screen of sixty meshes to the inch and yet be retained by one of seventy
meshes. The incrusting matter being finer than this, a perfect separation is obtained
at a very slight expense and by very simple means.
Dated this 3rd day of December 1888.
COMPLETE SPECIFICATION.
Improvements in the Method of and Apparatus for Effecting the
Separation of Iron or Iron Ores by Mechanical Means from
Associated Gangue.
I, BENJAMIN JOSEPH BARNARD MILLS of 23 Southampton Buildings, in the County
of Middlesex, Patent Agent, do hereby declare the nature of this invention, a com-
munication to me from abroad by Thomas Alva Edison, of Llewellyn Park, in the
County of Essex, and State of New Jersey, United States of America, Inventor,
and in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement :-
ง
The object of this invention is to effectively separate the iron in oolithic iron ores

page_text: from the earthy material thereof. This has been found very difficult to accomplish,
because the iron is not magnetic, and is in the form of small plates or tablets surrounded
by earthy matter, and if these are heated for the purpose of making the iron
magnetic, and then using magnets to effect the separation, the earthy matter hardens
and cakes upon and around the tablets, so that it cannot be entirely separated by the
magnet. I have therefore found it necessary to employ the mechanical process of
separation which constitutes my invention.
I first crush or pulverize the ore sufficiently to separate the tablets from one
another, and the earthy matter is then cleaned off the tablets by attrition of the
crystals upon one another and upon pieces of hard material. The mass of mingled
iron and earthy material is then placed in a screen, by which the fine particles of
earthy matter are separated from the iron tablets. The crystals or plates of oolithic
iron are very nearly of the same size, and in those from one mine for instance,
practically the whole of the plates will pass through a 60 mesh screen, and yet be
retained by one of 70 meshes. The incrusting matter being finer than this, a perfect
separation is obtained at very slight expense and by very simple means.
The
The apparatus for carrying out the invention is illustrated in the drawing. A. A are
rollers, between which the material is crushed, and from which it falls into a hopper 'B.
The revolving hollow cylinder 'C bas an opening in one side with a lid or cover at a
for closing it. A portion of material from the 'hopper is allowed to fall into this
cylinder, and such cylinder is then closed and revolved until, by friction, as just
described, the earthy matter is separated from the iron plates or tablets.
cylinder is finally turned so that the part a is over the 'hopper D, and it is then opened
and the material, except the large pieces 'is allowed to fall into this hopper, from
which it is gradually fed into the slowly revolving and slightly inclined, cylindrical
screen E, which has open ends, and as the material passes slowly down this screen,
it is sifted and separated as already explained, the iron tablets finally falling from
the lower end of the cylinder, while the fine particles of earthy matter fall on the
other side of the partition F.
Having now particularly described and ascertained the mature of any said inven-
tion, and in what manner the same is to be performed, 1 declare that what I
claim is:―
The method of effecting the separation of oolithic iron ores, by first crushing or
pulverizing the ore, then cleaning the crystals by attrition, and then separating them
from the rest by a screen, substantially as hereinbefore described.
Dated this 2nd day of September 1889.
Dated CRIS 200Y O September 1889.
B. J. B. MILLS.
By Harris & Mills,
.23, Southampton Buildings, London, Agents.

page_text: Date of Application, 3rd Dec., 1888
Complete Specification Left, 2nd Sept., 1889-Accepted, 5th Oct., 1889
PROVISIONAL SPECIFICATION.
Improvements in the Method of and Apparatus for Extracting Gold
from its Ore by Amalgamation.
I, BENJAMIN JOSEPH BARNARD MILLS of 23 Southampton Buildings, in the
County of Middlesex, Patent Agent, do hereby declare the nature of this invention, a
communication to me from abroad by Thomas Alva Edison of Llewellyn Park, in
the County of Essex, and State of New Jersey, United States of America, Inventor,
to be as follows:-
This invention relates to a process of treating ores of gold, which contain sulphur,
to extract the gold therefrom. Heretofore, as is well known, no satisfactory and
economical process of treatment for low grade sulphide ores has been devised.
This inventor's process is as follows: The gold ore is first crushed fine enough to
liberate the greater part of the gold particles. These gold particles appear to be
covered with an invisible envelope of some material which prevents amalgamation, and
so renders the ordinary processes of amalgamation unavailing. The inventor, after
pulverizing, concentrates the sulphides and removes the lighter matters therefrom by
water concentration in jigging or vanning machines in the usual manner.
A suitable quantity of the concentrated ore is then placed in a weak solution of
nitric acid, containing also a small quantity of nitrate of mercury. This, after a time,
by the action of the nitric acid, removes the film from the particles and causes their
surfaces to become fully amalgamated. As much of the solution as possible is then
drawn off, and the remaining mass is placed in a centrifugal drier, and being whirled
around with great force, the solution is thrown off and the ore left dry. The solution
is collected and used over again, a little acid being added each time to make up for
loss by evaporation.
Instead of the centrifugal drier, the process of water displacement may be employed
for removing and saving the expensive solution. The material is placed in a vessel
and water admitted above it and the air exhausted at the bottom of the vessel, where-
upon the water filters through and displaces the acid without mixing with it, the acid
passing off through an outlet and being preserved.
The ore, after the solution is removed from it, may be amalgamated in any ordinary
manner, the previous partial amalgamation making the final amalgamation more rapid
and effectual.
1
1 1
1000
COMPLETE SPECIFICATION.
Improvements in the Method of and Apparatus for Extracting Gold
from its Ore by Amalgamation.
I, BENJAMIN JOSEPH BARNARD MILLS of 23 Southampton Buildings, in the County
of Middlesex, Patent Agent, do hereby declare the nature of this invention, a com-
munication to me from abroad by Thomas Alva Edison, of Llewellyn Park, in the
County of Essex, and State of New Jersey, United States of America, Inventor, and
in what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:—
This invention relates to a process of treating ores of gold which contain sulphur,
to extract the gold therefrom.

page_text: Heretofore, as is well known, no process has been devised by which the gold could
be economically extracted from low grade sulphide ores.
Ordinary amalgamation is not successful, because the gold appears to be coated
with an invisible envelope of material, which prevents amalgamation, and when it is
attempted to obviate this difficulty by grinding the gold in amalgamating pans,
excessive grinding is required and the mercury becomes floured, and very little gold
is obtained. If it is attempted to roast the ore before amalgamating, the free
sulphur formed in roasting will sulphurize the mercury and flour it, and thus prevent
amalgamation.
Another process is that of roasting the ore and dissolving out the gold by means of
chlorine gas, but this is an expensive process, requiring a large investment in plant
and highly skilled experts, and it has therefore never been successful to any great
extent.
The exact nature of the fine film upon the globe has not yet been satisfactorily
determined. An Australian investigator has reported it to be sulphide of gold, but
there seems to me some reason to suppose it otherwise, and I cannot state positively
'what it is.
My process is based upon the fact that tho coating upon the gold may be removed
by the application of weak nitric acid, and that at the same time the surface of the
gold may be amalgamated, if there is added to the weak acid solution, a small quantity
of a mercurial salt, especially nitrate of mercury.
The process is as follows. The gold bearing ore is first crushed in the ordinary
manner to such a degree of fineness as will practically liberate the greater part of the
particles of gold. Then, by water concentration, as by the use of jigging or van-
ning machines, the lighter matters are removed from the pulverized mass, and the
sulphides are concentrated. When in this state, the sulphur of the sulphides is
inactive on the nitrate of mercury solution, only the film on the gold being attacked
thereby.
A suitable quantity of the concentrated ore, several tons of it if desired, is then
thrown into a suitable vat and the weak solution of nitric acid, which preferably
contains also a small quantity of nitrate of mercury, is run on to it, preferably so as
to just cover it. I have found that the application of the solution for about one hour
is sufficient to remove the external film, and to cause all the gold particles to become
fully amalgamated upon their surfaces. As much of the solution as possible is then
drawn off, and the remaining mass of pulp is shovelled into a centrifugal drying
machine of the well known character employed in various other processes, such as the
manufacture of sugar. The pulp being whirled around in the machine with great
velocity, the centrifugal force throws the solution off the ore, leaving it entirely dry.
The solution, being collected, is saved to be used over again, a small quantity of acid
being added to make up for loss due to evaporation, and also if required a small
quantity of nitrate of mercury.
Instead of this there may be employed, for the purpose of removing and saving the
expensive acid solution, the process of displacement by water. The pulp being placed
in a vessel and water admitted above it, and the air exhausted at the bottom of the
vessel, the water will, as is well known, filter through the pulp and displace the
acid without mixing with it, the acid passing off through an outlet at the bottom
and being preserved for the next operation.
The ore, being removed from the centrifugal machine, or the displacing vessel,
may now be amalgamated in any ordinary manner, either in an amalgamating pan or
by running it over amalgamating plates, and in a few minutes the gold will combine
wholly with the mercury, from whence it will afterwards be recovered in any ordinary
manner.
It is evident that the process can be carried out without the addition to the solution
of the mercurial salt, the whole amalgamation being then accomplished afterward in
the amalgamating pans or otherwise, but the previous surface amalgamation makes the
final amalgamation more rapid and effectual, and the nitrate of mercury also assists

page_text: in the removal of the film from the gold particles, and since the mercury is all retained
by the gold, so that it is ultimately saved, it is beter to use it.
The strength of the solution employed depends to a great extent upon the character
of the ore to be treated.
With the ordinary concentrated sulphurets, a solution of 100 parts of water,
10 parts of ordinary nitric acid, and 5 parts of nitrate of mercury will be sufficient,
but in some instances, the pulp will contain, even after concentration, matters
which will reduce the nitric acid as well as the mercury, and thus in such cases
a larger quantity of each of these ingredients will be required, the amount of
which in each particular instance can be determined only. by practice. The solution
should however always be so weak as not to materially attack any portion of the
pyrites.
It will be seen that there is thus provided a commercially practicable method of
working low grade ores, by which the economical use of expensive re-agents such as
nitric acid, is made possible, since the use of the centrifugal drier, or of the displacing
process, allows all or practically all of the solution to be removed and saved, and thus
the cost of the chemical agents required per ton of ore, is reduced to an insignificant
amount, and since the chemical amalgamation of the surface of the gold renders all
grinding before the final amalgamation unnecessary.
As has been stated, the nitrate of mercury helps to reduce the refractory film on
the gold particles, and it is possible therefore to use this material alone without any
acid; it however much less rapid and effectual.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to he performed, I declare that what I
claim is :-
The method of treating auriferous sulphurets by concentrating the sulphurets,
acting upon them with nitric acid and nitrate of mercury, removing and collecting
the solution by a centrifugal drier or by water displacement, and then amalgamating
the gold, substantially as hereinbofore described.
Dated this 2nd day of September 1009.
5 2nd day of September Loo9.
B. J. B. MILLS.
By Harris & Mills,
23, Southampton Buildings, London, Agents.

page_text: Date of Application, 3rd Dec., 1888
Complete Specification Left, 2nd Sept., 1889-Accepted, 5th Oct., 1889
PROVISIONAL SPECIFICATION.
Improvements in Methods of and Apparatus for Separating Ores or
Metals from Associated Gangue.
I, BENJAMIN JOSEPH BARNARD MILLS of 23 Southampton Buildings, in the County
of Middlesex, Patent Agent, do hereby declare the nature of this invention, a com-
munication to me from abroad by Thomas Alva Edison, of Llewellyn Park, in the
County of Essex, and State of New Jersey, United States of America, Inventor, to
be as follows :-
The object of this invention is to provide for the easy and economical separation of
ores or metals from associated gangue, especially in those classes of ores where the
separation has been so difficult and expensive a process that it has been found
impossible or undesirable to utilize such ores. The inventor employs the process of.
magnetic separation, in which mingled magnetic and non-magnetic particles arc
caused to fall past the poles of a magnet, which alters the trajectory or direction of
falling of the magnetic particles, so that these fall into a different receptacle from that
which the non-magnetic ones go to, and the invention consists in improvements upon
the apparatus for this purpose and upon the way or method of preparing the materials
for use in such apparatus, designed to render the whole process more rapid, effectual,
and economical.
A portion of the invention relates to the receptacle or hopper from which the
mingled materials are allowed to fall past the magnet poles. Before this invention,
hoppers with flaring sides, converging to an opening at the bottom, have been used,
but it is found that with these the normal fall of the particles is not in a straight
line, but that they fall in different angular directions and spread out into an irregular
mass, which makes it very difficult to act upon them by the magnet.
This difficulty the inventor remedies by using a hopper with a flat bottom, which
has at its middle part a very narrow opening or openings. There may be à line of
small holes across the bottom of the hopper or a single narrow slit. It is found best
to make the bottom of the hopper of a thin sheet of brass. When the line of small
holes is used, the material falls in a number of distinct vertical streams and these
remain separated for a foot or more below the hopper, but the particles, being gradually
spread apart by the effect of the air, the streams are merged into one wide thin
mass, the particles composing which are separated from one another, which makes it
easy for the magnet to act upon them, so that the direction of falling of the magnetic
particles is altered, and they are readily and completely separated from those which
are non-magnetic.
When the pulverized ore or other material to be acted upon is very finely divided
the holes must be very small. For material capable of passing through a screen of
100 meshes to the inch, the holes should be 3-64 of an inch in diameter and 1-32 of
an inch apart. But the size of the openings must of course be varied according to
the character of the material, and for 20 mesh ore they may be of an inch wide.
When the holes are so small it may be difficult for the particles to pass through
then, and in this case, to assist the discharge, means are provided for rapidly vibrating
the bottom plate of the hopper, whereby the particles of material are vibrated or
agitated which causes them to be discharged freely.
If, instead of the line of holes, a single narrow slit is used it should be about 3-64
of an inch wide for 100 mesh material.
When the body of mingled magnetic and non-magnetic materials, which falls from
the hopper as above described, contains many particles of very light substance, as is
the case with certain iron-ores, which contain light particles of phosphorous and

page_text: silicon ores, it is very difficult to effectively separate such light particles from the
magnetic material, because they are affected by currents of air, and so may float or
be carried into the receptacle for the magnetic particles, whereby the product is
rendered impure and unavailable for the Bessemer process of making steel.
The inventor obviates this difficulty by employing a gentle current of air affecting
the stream of materials as it falls from the hopper whereby these extremely light
particles are separated from the rest and directed into a separate receptacle which is
provided for them.
A pipe extends from a suitable fan or blower and terminates in a cross pipe having
an aperture or series of apertures in one side, and extending along the whole width
of the falling mass, so that the gentle air current is directed equally against the whole
stream. An inclined partition extends down from the opposite side of the stream so
that the light particles are urged over the edge of this partition into their own recep-
tacle while the rest of the mixture falls past the magnet, which draws the magnetic
particles aside and causes them to fall into their proper place, the heavier non-mag-
netic particles continuing to fall in a straight line.
But instead of this the stream
may fall past an opening in an air tight chamber, from which chamber the air is
continually exhausted by an air pump, and the current of air produced by the suction
separates the light particles from the rest and draws them into the chamber:
While, as above mentioned, a magnet is used to effect the separation, it is possible
in some cases to use an electrified or statically charged body as the attracting means.
Also, a permanent magnet may be employed. It is generally best however to use an
electro magnet and more especially the inventor prefers to use a bar magnet or open
ended magnet rather than a horse shoe magnet. The reason for this is that the mag-
netic field of a horse shoe magnet is small and concentrated and does not include a
large quantity of the falling material, but with a flat bar magnet whose active pole is
as wide as the wide thin stream of falling particles, the magnetic field is very much
spread out and acts upon the falling stream throughout a large portion of its extent,
and the magnetism impressed on the magnetic particles, while sufficient to alter their
trajectory is at no time of sufficient strength to cause such particles to mutually attract
each other and thus lock the non-magnetic particles between them and carry such
non-magnetic particles into the wrong receptacle.
The apparatus above described may be employed to effect the separation of any
mingled magnetic and non-magnetic substances in a finely divided condition and
especially for magnetic iron ores. Haematite iron ores,, which are not magnetic may
be first finely pulverized, then heated to a white heat, and then cooled. This makes
the iron magnetic and it may be separated from the non-magnetic portion of the ore
as above described. But the same effect may be produced by heating the ore to a red
heat only, if, in heating, the ore is placed in an atmosphere of a roducing agent such
as carbon monoxide. The pulverized ore is in this case mixed with a small quantity
of charcoal or other carbon and heated in a chamber to which the air has only slight
access. This air combines with the carbon to form carbon monoxide and this reduces
the surfaces of the iron particles to magnetic oxide and enables them to be used with
the magnetic separator.
To enable the magnetic separator to be employed with non-magnetic metals, such as
gold and silver, the inventor first pulverizes the gold and silver ore to such a degree
of fineness as to detach the particles of metal from the rest. The mingled mass of
particles of precious metal and of quartz, rock, sand, or other non-electrical conducting
and non-magnetic material, is placed in an electrolytic bath containing a solution of
a salt of iron and having positive and negative electrodes of iron, and on an electric
current being passed through such bath, a slight deposit of iron is formed on one
side. only of each of the metal particles, and in a short time sufficient magnetic
material is added to the gold to permit it to be readily effected by a magnet. The
inventor has found that the presence of sand and like materials in the bath increases
rather than diminishes the effect on the gold. After the process has been continued
for several hours the whole mass is removed from the bath, dried, preferably in a

page_text: centrifugal drier, so that the iron solution may be used over again, sifted, and then
acted upon by the magnetic separator whereby the gold iron particles are removed
from the non-magnetic material. The gold may then be readily separated from the
iron by fusion.
نو
1000
COMPLETE SPECIFICATION.
Improvements in Methods of and Apparatus for Separating Ores or
Metals from Associated Gangue.
I, BENJAMIN JOSEPH BARNARD MILLS of 23 Southampton Buildings, in the County
of Middlesex, Patent Agent, do hereby declare the nature of this invention, a com-
munication to me from abroad by Thomas Alva Edison of Llewellyn Park, in the
County of Essex, and State of New Jersey, United States of America, Inventor, and
in what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement :-
The object of this invention is to provide for the easy and economical separation of
ores or metals from associated gangue, especially in those classes of ores where the
separation has been so difficult and expensive a process that it has been found
impossible or undesirable to utilize such ores. The inventor employs the process of
magnetic separation, in which mingled magnetic and non-magnetic particles are caused
to fall past the poles of a magnet, which alters the trajectory or direction of falling
of the magnetic particles, so that these fall into a different receptacle from that which
the non-magnetic ones go to, and the invention consists in improvements upon the
apparatus for this purpose and upon the way or method of preparing the materials
for use in such apparatus, designed to render the whole process more rapid, effectual,
and economical.
A portion of the invention relates to the receptacle or hopper from which the mingled
materials are allowed to fall past the magnet poles. Before this invention, hoppers
with flaring sides converging to an opening at the bottom have been used, but it is
found that with these, the normal fall of the particles is not in a straight line, but
that they fall in different angular directions and spread out into an irregular mass,
which makes it very difficult to act upon them by the magnet.
This difficulty the inventor remedies by using a hopper with a flat bottom, which
has at its middle part, a very narrow opening or openings. There may be a line of
small holes across the bottom of the hopper or a single narrow slit. It is found best
to make the bottom of the hpper of a thin sheet of brass. When the line of small
holes is used, the material falls in a number of distinct vertical streams, and these
remain separated for a foot or more below the hopper, but the particles being gradually
spread apart by the effect of the air, the streams are merged into one wide thin
mass, the particles composing which are separated from one another, which makes it
easy for the magnet to act upon them, so that the direction of falling of the magnetic
particles is altered, and they are readily and completely separated from those which
are non-magnetic.
When the pulverized ore or other,material to be acted upon is very finely divided,
the holes must be very small. For material capable of passing through a screen of
100 meshes to the inch, the holes should be of an inch in diameter and 3 of an
inch apart. But the size of the openings must of course be varied according to the
character of the material, and for 20 mesh ore, they may be of an inch wide.
When the holes are so sinall it may be difficult for the particles to pass through
them, and in this case, to assist the discharge, means are provided for rapidly vibrating
the bottom plate of the hopper, whereby the particles of material are vibrated or
agitated, which causes them to be discharged freely.

page_text: If instead of the line of holes, a single narrow slit is used, it should be about
of an inch wide for 100 mesh material.
This portion of the invention is illustrated in figures 1 to 6 of the accompanying
drawing.
Figure 1 is a view, principally in vertical section, of magnetic separating apparatus
embodying this part of the invention. Figure 2 illustrates one form for the bottom
of the hopper. Figure 3, the bottom of the hopper in the form employing a narrow
slit. Figure 4 shows one way of vibrating the hopper. Figure 5 shows another
way, and Figure 6 is a somewhat exaggerated view in section of a portion of the
hopper in the first form.
A represents a straight sided box or hopper, whose bottom is a thin metal plate B.
This chamber may be placed at or near the top of a closed chamber C, or the material
miayfall in the open air. Below the hopper is placed an electro-magnet D, so that the
material falling from the hopper, falls past the poles of said magnet. Below the
magnet are placed, two bins or receptacles E and E. It will be understood that
when a stream of mingled magnetic and non-magnetic particles falls froin the hopper,
the attraction of the magnet alters the direction of falling of the magnetic particles,
so that these fall into the receptacle E, while the non-magnetic portion of the mixture
falls vertically into receptacle E.
The bottom B of the hopper has either a row of small holes a. a across its middle
part, as shown in figures 1, 2, 4 and 6, or a single narrow slit b, as in figures 3 and 5.
In figures 2, 3, 4 and 5, the openings are shown at about their actual preferred
width in practice, but it will be understood that this is entirely out of proportion to
the size shown for the hopper, that is, the hopper will be very much larger in pro-
portion to the size of the holes than it is shown, and there will be very many more
holes in the row. And in figures 3 and 5, the slit bis shown at about its actual
diameter, but it will of course be much longer proportionately than it is shown.
Figure 6 shows approximately how the material falls from the holes. In this
figure the holes are shown at about twice their preferred actual diameter for 100 mesh
material. The mingled material, of which the hopper is kept full, falls through each
hole in a straight stream, such streams being at first distinct from one another, but
the particles gradually spread out, so that at a distance of about a foot from the
hopper, the streams all unite into a wide thin sheet, the particles composing which are
separated from one another. At this point is placed the magnet which draws the
magnetic particles aside from the rest as illustrated in figure 1.
As stated, it is best in some cases to vibrate the bottom of the hopper. One way
of doing this is shown in figures 1 and 4.
F is a roller, which is revolved by suitable power, and which is covered with leather
coated with resin. Over the roller F are stretched a number of wires c, c, which are
attached to the bottom plate of the hopper, and whose other ends are rigidly secured,
preferably adjustably, by screws d.
It will be seen that the turning of the wheel under the wires will give them longi-
tudinal vibrations, which will give molecular vibrations to the plate of the hopper, and
the vibrations thus given to the particles of the material will cause the same to fall
freely through the openings.
Another way of vibrating the hopper is shown in figure 5. Several small electro
magnets G. G. have movable armatures mechanically connected with the bottom of
the hopper, and the circuits of these magnets are all controlled by a rotating circuit
making and breaking wheel, so that said armatures are caused to vibrate and throw
the plate B into vibrations.
When the body of mingled magnetic and non-magnetic materials, which falls from
the hopper as above described, contains many particles of very light substance, as is
the case with certain iron ores which contain light particles of phosphorous and
silicon ores, it is very difficult to effectively separate such light particles from the
magnetic material, because they are affected by currents of air and so may float or
be carried into the receptacle for the magnetic particles, whereby the product is
rendered impure and unavailable for the Bessemer process of making steel,

page_text: The inventor obviates this difficulty by employing a gentle current of air affecting
the stream of materials as it falls from the hopper, whereby these extremely light
particles are separated from the rest and directed into a separate receptacle which is
provided for them.
A pipe extends from a suitable fan or blower and terminates in a cross pipe having
an aperture or series of apertures in one side, and extending along the whole width
of the falling mass, so that the gentle air current is directed equally against the whole
stream. An inclined partition extends down from the opposite side of the stream, so
that the light particles are urged over the edge of this partition into their own
receptacle, while the rest of the mixture falls past the magnet, which draws the
magnetic particles aside and causes them to fall into their proper place, the heavier
non-magnetic particles continuing to fall in a straight line. But instead of this, the
stream may fall past an opening in an air tight chamber, from which chamber the air
is continually exhausted by an air pump, and the current of air produced by the
suction separates the light particles from the rest and draws them into the chamber.
While, as above mentioned, a magnet is used to effect the separation, it is possible
in some cases to use an electrified or statically charged body as the attracting means.
Also, a permanent magnet may be employed. It is generally best however to use an
electro-magnet, and more especially the inventor prefers to use a bar magnet or open
ended magnet, rather than a horse shoe magnet. The reason for this is that the
magnetic field of a horse shoe magnet is small and concentrated and does not include
a large quantity of the falling material, but with a flat bar magnet, whose active pole
is as wide as the wide thin stream of falling particles, the magnetic field is very
much spread out and acts upon the falling stream throughout a large portion of its
extent, and the magnetism impressed on the magnetic particles, while sufficient, to
alter their trajectory, is at no time of sufficient strength to cause such particles to
mutually attract each other and thus lock the non-magnetic particles between them
and carry such non-magnetic particles into the wrong receptacle.
The features just described are illustrated in figures 7 and 8 of the drawing.
Figure 7 is a vertical section and partial side elevation of the magnetic separator,
and Figure 8 is a perspective view of the same.
A short distance below the hopper is placed the magnet B, which is a wide flat
bar magnet, whose pole extends the whole width of the stream which falls from the
hopper. is a pipe which extends from a suitable fan or blower adapted to produce
a gentle current of air. This pipe is divided into two branch pipes D and D¹.
Pipe D extends beneath the hopper, a short distance below it, and terminates in a
long cross pipe E, which extends the whole width of the hopper, and is provided with
an aperture or series of apertures, through which the current of air is directed against
the falling particles. The pipe D' extends below the magnet B, and terminates in a
cross pipe E', whereby the air current is also directed against the falling particles at
this point. On the other side of the opening in the hopper, and just below the
pipes D and D', are placed inclined partitions F and F. It will be seen that as the
stream of mingled magnetic and non-magnetic particles falls from the hopper, the air
current from the pipe E will separate from it the very light non-magnetic particles,
and these will pass to the left of the partition F and fall into the receptacle formed
by said partition. Any light particles which are not removed at this point, will
receive the air current from the pipe El and be blown past the partition F¹. The
magnet B, as will be well understood, alters the direction of falling of the magnetic
portion of the material, so that it falls to the right of the partition G, while the non-
magnetic particles which are too heavy to be affected by the air current will fall
vertically from the hopper into the space between partitions F1 and G.
The widely
diffused magnetic field of the bar magnet acts upon the material more effectively than
the concentrated field of a horse shoe magnet, as already explained.
The dotted lines in figure 7 illustrate a modification of the invention. An air-
tight chamber is provided with an opening in proximity to the falling stream, and a
pipe H leads from this chamber to an exhausting apparatus. Air being constantly
withdrawn from the chamber, the air current produced by the suction, acts upon

page_text: the light particles and draws them into the chamber. The chamber between
partitions and G may also be made air-tight and provided with an exhaust pipe,
with a similar result.
The apparatus above described may be employed to effect the separation of any
mingled magnetic and non-magnetic substances in a finely divided condition, and
especially for magnetic iron ores. Haematite iron ores which are not magnetic, may
be first finely pulverized, then heated to a white heat, and then cooled. This makes.
the iron magnetic and it may be separated from the non-magnetic portion of the ore
as above described. But the same effect may be produced by heating the ore to a
red heat only, if in heating, the ore is placed in an atmosphere of a reducing agent,
such as carbon monoxide. The pulverized ore, is in this case, mixed with a small
quantity of charcoal or other carbon, and heated in a chamber to which the air has
only slight access. This air combines with the carbon to form carbon monoxide, and
this reduces the surfaces of the iron particles to magnetic oxide and enables them to
be used with the magnetic separator.
To enable the magnetic separator to be employed with non-magnetic metals, such
as gold and silver, the inventor first pulverizes the gold and silver ore to such a
degree of fineness as to detach the particles of metal from the rest.
The mingled
mass of particles of precious metal and of quartz, rock, sand, or other non-electrical
conducting and non-magnetic material, is placed in an electrolytic bath, containing a
solution of a salt of iron, and having positive and negative electrodes of iron, and on
an electric current being passed through such bath, a slight deposit of iron is formed
on one side only of each of the metal particles, and in a short time sufficient magnetic
material is added to the gold to permit it to be readily affected by a magnet. The
inventor has found that the presence of sand and like materials in the bath, increases
rather than diminishes the effect on the gold. After the process has been continued
for several hours, the whole mass is removed from the bath, dried, preferably in a
centrifugal drier, so that the iron solution may be used over again, sifted, and then.
acted upon by the magnetic separator, whereby the gold-iron particles are removed
from the non-magnetic material. The gold may then be readily separated from the
iron by fusion.
This process is illustrated in figures 9, 10 and 11 of the drawing.
Figure 9 is an illustration of the principle of the invention. Figure 10 is a cross
section, and Figure 11 a top view of the electrolytic cell, such as the inventor prefers
to use in practice.
In figure 9, A represents a cell, B a solution therein of a salt of iron, a, a positive
and negative electrodes of iron connected with a source of electricity, represented at C,
and b, metal particles placed in the cell between the electrodes.
The inventor has found that when any piece of metal, no matter how small, is
placed in this way between the electrodes of an electrolytic cell, there will be a deposit
produced upon one side thereof only. There is a convergence of the conducting
lines from the poorly conducting liquid to the highly conducting metal, and a sharp
difference of potential between the liquid and the metal at the points where the current
enters and leaves the metal, so that there must be a deposit of metal on the side where
the current enters the particle.
In figure 9, the convergence of the lines of conduction is indicated, and the heavy.
shading on one side of each of the particles b. b (whose size is of course exaggerated
in the drawing) indicates the deposit on such particles.
In figures 10 and 11, E represents a tank of iron or other suitable metal, which
is electrically divided longitudinally into two parts, such parts being separated by
wooden or other insulating strips c, and secured together by being bolted to heavy
planking d at the bottom and ends of the tank. The tank may be pivotted upon
trunnions e, e, supported by standards at the ends of the base or bed plate F, so that
the tank may be turned to dump its contents.
Within the tank, and supported from the sides thereof, are iron plates f and f¹, the
plates being alternately positive and negative, and connected alternately to opposite
sides of the tank, by which they are supported. Connections may be made to the

page_text: tank by springs g, g bearing on the trunnions; these trunnions enter or are joined to
iron plates h, h, at the ends of the tank, and at each end, one of the securing bolts i
passes through the planking into the tank, while the other bolt only enters such
planking, whereby one side of the tank becomes positive and the other negative, they
being connected only through the contents of the tank. The tank may be made large
enough to contain several tons of powdered ore, and it is best to have the plates about
one eighth of an inch apart.
In the tank so constructed, or in one of other convenient constructions, is placed a
solution of a salt of iron, preferably sulphate of iron.
There is then placed in the tank, the mixture of gold and gangue, the same being
pulverized or reduced to a finely divided condition, so that the particles of gold are
in a free state. As the current is passed through the tank, all the particles of gold
between the iron plates receive a slight deposit of iron in the manner already
explained.
It is best to continue the process for several hours, after which the whole mass is
furned out, preferably into a centrifugal drier. The pulp is dried and sifted, and then,
by magnetic attraction, the gold is separated from the ore or gangue.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is.
1. In a magnetic separator in which a stream of mingled magnetic and non-
magnetic particles falls past the poles of a magnet, which alters the direction of
falling of the magnetic particles, the hopper for delivering the material, which has a
flat bottom containing a single narrow slit or a row of small holes, the devices for
vibrating the hopper, the means for producing a gentle air current upon the falling
material, and the wide flat bar magnet whose pole extends across the whole width of
the falling stream, substantially as hereinbefore described.
2. The method of separating the precious metals from their ores, by finely pul-
verizing the ore, depositing iron electrolytically upon the metal particles, and then
separating these from the rest by the magnetic separator, substantially as hereinbefore
described.
3. The method of treating haematite iron ores by finely pulverizing the ore, heating
it, allowing it to cool, and then separating the iron from the rest by the magnetic
separator, substantially as hereinbefore described.
Dated this 2nd day of September 1889
Dated this 2nd day of September 1889.
B. J. B. MILLS.
By Harris & Mills,
23, Southampton Buildings, London, Agents.