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|Atomic Number:||57||Atomic Symbol:||La|
|Atomic Weight:||138.9055||Electron Configuration:||2-8-18-18-9-2|
|Melting Point:||920oC||Boiling Point:||3469oC|
|Description:||Soft silvery white transition metal.|
|Uses:||Found with rare earths in monazite and bastnasite|
History(Greek lanthanein, to lie hidden) Mosander in 1839 extracted a
new earth lanthana, from impure cerium nitrate and recognized the new element.
Lanthanum was isolated in relatively pure form in 1923. Iron exchange and
solvent extraction techniques have led to much easier isolation of the so-called
SourcesLanthanum is found in rare-earth minerals such as cerite,
monazite, allanite, and bastnasite. Monazite and bastnasite are principal ores
in which lanthanum occurs in percentages up to 25 percent and 38 percent
respectively. Misch metal, used in making lighter flints, contains about 25
The availability of lanthanum and other rare earths has improved greatly in
recent years. The metal can be produced by reducing the anhydrous fluoride with
PropertiesLanthanum is silvery white, maleable, ductile, and soft
enough to be cut with a knife. It is one of the most reactive of the rare-earth
metals. It oxidizes rapidly when exposed to air. Cold water attacks lanthanum
slowly, while hot water attacks it much more rapidly.
At 310C, lanthanum changes from a hexagonal to a face-centered cubic
structure, and at 865C it again transforms into a body-centered cubic structure.
IsotopesNatural lanthanum is a mixture of two stable isotopes, 138La
and 139La. Twenty three other radioactive isotopes are recognized.
UsesRare-earth compounds containing lanthanum are extensively used in
carbon lighting applications, especailly by the motion picture industry for
studio lighting and projection. This application consumes about 25 percent of
the rare-earth compounds produced. La2O3 improves the alkali resistance of
glass, and is used in making special optical glasses. Small amounts of
lanthanum, as an additive, can be used to produce nodular cast iron.
There is current interest in hydrogen sponge alloys containing lanthanum.
These alloys take up to 400 times their own volume of hydrogen gas, and the
process is reversible. Every time they take up the gas, heat energy is released;
therefore these alloys have possibilities in an energy conservation system.
HandlingLanthanum and its compounds have a low to moderate acute
toxicity rating; therefore, care should be taken in handling them.
CostsThe metal costs about $5/g.