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|Atomic Number:||27||Atomic Symbol:||Co|
|Atomic Weight:||58.9332||Electron Configuration:||2-8-15-2|
|Melting Point:||1495oC||Boiling Point:||2870oC|
|Uses:||permanent magnets, used in alloys, radioactive
History(Kobald, from the German, goblin or evil spirit, cobalos, Greek,
mine) Brandt discovered cobalt in about 1735.
SourcesCobalt occurs in the minerals cobaltite, smaltite, and
erythrite, and is often associated with nickel, silver, lead, copper, and iron ores, from which it is
most frequently obtained as a by-product. It is also present in meteorites.
Important ore deposits are found in Zaire, Morocco, and Canada. The U.S.
Geological Survey has announced that the bottom of the north central Pacific
Ocean may have cobalt-rich deposits at relatively shallow depths in water close
to the the Hawaiian Islands and other U.S. Pacific territories.
PropertiesCobalt is a brittle, hard metal, resembling iron and nickel
in appearance. It has a metallic permeability of about two thirds that of iron.
Cobalt tends to exist as a mixture of two allotropes over a wide temperature
range. The transformation is sluggish and accounts in part for the wide
variation in reported data on physical properties of cobalt.
UsesIt is alloyed with iron, nickel and other metals to make Alnico, an
alloy of unusual magnetic strength with many important uses.
Stellite?? alloys, containing cobalt, chromium,
and tungsten, are used for high-speed, heavy-duty, high
temperature cutting tools, and for dies.
Cobalt is also used in other magnetic steels and stainless steels, and in
alloys used in jet turbines and gas turbine generators. The metal is used in
electroplating because of its appearance, hardness, and resistance to oxidation.
The salts have been used for centuries to producte brilliant and permanent
blue colors in porcelain, glass, pottery, tiles, and enamels. It is the
principal ingredient in Sevre's and Thenard's blue. A solution of the chloride
is used as a sympathetic ink. Cobalt carefully used in the form of the chloride,
sulfate, acetate, or nitrate has been found effective in correcting a certain
mineral deficiency disease in animals.
Soils should contain 0.13 to 0.30 ppm of cobalt for proper animal nutrition.
Cobalt-60, an artificial isotope, is an important gamma ray source, and is
extensively used as a tracer and a radiotherapeutic agent.
CostsSingle compact sources of Cobalt-60 vary from about $1 to
$10/curie, depending on quantity and specific activity.
HandlingExposure to cobalt (metal fumes and dust) should be limited to
0.05 mg/m^3 (8-hour time-weighted average 40-hour week).