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(Samarskite, a mineral) Discovered spectroscopically by its sharp absorption lines in
1879 by Lecoq de Boisbaudran in the mineral samarskite, named in honor of a Russian mine
official, Col Samarski.
Samarium is found along with other members of the rare-earth elements in many minerals,
including monazite and bastnasite, which are commercial sources. It occurs in monazite to
the extent of 2.8%. While misch metal containing about 1% of samarium metal, has long been
used, samarium has not been isolated in relatively pure form until recent years.
Ion-exchange and solvent extraction techniques have recently simplified separation of the
rare earths from one another; more recently, electrochemical deposition, using an
electrolytic solution of lithium citrate and a mercury electrode, is said to be a simple,
fast, and highly specific way to separate the rare earths. Samarium metal can be produced
by reducing the oxide with lanthanum.
Samarium has a bright silver luster and is reasonably stable in air. Three crystal
modifications of the metal exist, with transformations at 734 and 922oC. The metal ignites in air at about 150oC. The sulfide has excellent
high-temperature stability and good thermoelectric efficiencies up to 1100oC.
Twenty one isotopes of samarium exist. Natural samarium is a mixture of several
isotopes, three of which are unstable with long half-lives.
Samarium, along with other rare earths, is used for carbon-arc lighting for the motion
picture industry. SmCo5 has
been used in making a new permanent magnet material with the highest resistance to
demagnetization of any known material. It is said to have an intrinsic coercive force as
high as 2200 kA/m. Samarium oxide has been used in optical glass to absorb the infrared.
Samarium is used to dope calcium fluoride crystal for use in optical lasers or lasers.
Compounds of the metal act as sensitizers for phosphors excited in the infrared; the oxide
exhibits catalytic properties in the dehydration and dehydrogenation of ethyl alcohol. It
is used in infrared absorbing glass and as a neutron absorber in nuclear reactors.
The metal is priced at about $5/g.
Little is known of the toxicity of samarium; therefore, it should be handled carefully.
Sources: CRC Handbook of Chemistry
and Physics and the American Chemical Society.
Last Updated:12/19/97, CST Information Services Team