The Parker post., 1918-11-09
THE F[OTAT|0N
METHOD EXCELS
(By Irving A. Palmer. }

The concentration of ores by fota-
ton is undoubtedly the most import
ant development in metallurgy since
the Introduction of the cyanide pro-
cess Although it is but seven years
since the first successful froth fiota-
tion plant in the United States was
built yet the tonnage of ore now con-
centrated in the country by this
method exceeds that treated by any
other non-ferrOus metallurgical pro-
cess. At the beginning of 1917 it was
estimated that more than 3O,O0O,O00
tons of ore was annually concentrated
by fiotation in the United States. This
tonnage exceeded that of all the cop
per smelters or of all the gravity con-
Icentration plants. Since that time the
percentage in favor of fiotation has no
doubt increased No other metallurgi-
cal process has ever made such head
way in so short period. AT present
1t is used with success In almost
every mining district In the world
where concentration is practiced.
In the fiotation process the valuable
minerals of an ore are separated from
the gangue or worthless portions by
causing them to float on water, while
the gangue sinks to the bottom. Az
the valuable minerals are usually
| heavier than the gangue minerals it
will be seen that fotation reverses the
principle of gravity concentration, In
which the heavier minerals go to the
bottom and the lighter ones above are
washed away. The seeming impossi-
bility of causing heavy minerals to
| float is accomplished in a number OF
ways, the underlying principles Of
which have never been thoroughly
explained. In spite of the fact that
millions of tons of ore are concentra-
ted by flotation no one yet fully un-
derstands why certain minerals can
be made to float while others cannot.
The absence of a satisfactory working
theory has rendered progress in the !
art largely matter of patient ex-
perimenting.
If quantity of pulverized ore con-
tanning metallic sulphides or free
metals be agitated in water contain
ing small amount of oil it Is found
that the oil shows tendency to con-
centrate on the surface of the sui
phides or of the free metals and out
on the particles of oxidized minerals
or of the gangue. On the other hand,
the water shows tendency to adhera
to, or to wet, the oxidized minerals
and the gangue. If. now. by means
of agitation, or by the blowing In
of air, bubbles are produced in the
liquid it will be found that the
oiled particles of sulphide or metal
tend to collect on the surfaces
of the bubbles, and that the
sulphide-laden bubbles tend to coal
ese into froth which floats ON the
surface and cannot be removed. The
particles of oxidized mineral and of
gangue, not being oiled. are not at
tracted to the bubbles and hence sink
to the bottom. In many cases fota-
tion can be effected by the use of an
acid which generates bubbles of gas
to which the sulphide particles adhere
and for which the particles of oxidiz
ed minerals and gangue have no par
ticular attraction. In brief, CONNER
cial flotation is based upon the selec-
tive affinity of air or gas bubbles for
particles of sulphide mineral or OF
metal which may or may not be. oiled.
Other substances than oils and acids
have been used successfully in pro-
ducing flotation, and good sepa-
rations have been made by using
any one or more of many differ
ent oils, acids, and other compounds,
and by applying agitation and aera-
tion in dozens of different ways.
But the real reason as to why
some substances are better than
others, or as to why some minerals
float and others do not, are as yet 'un-
known. The most that can be said
at present is that metals and sulphide
minerals with metallic luster usually
can be made to float, but oxidized
metallic minerals and gangue cannot.
However mercury sulphide, which has
no luster, and graphite, which has a
luster, but which is not a sulphide,
are both susceptible to fiotation.
Only by trial is it possible to deter
mine what can be done with any
given minaral -.