Lanthanum is a silvery white metallic element belonging to group 3 of the periodic table and often considered to be one of the lanthanides. Found in some rare-earth minerals, usually in combination with cerium and other rare earth elements. Lanthanum is malleable, ductile, and soft enough to be cut with a knife. It is one of the most reactive of the rare-earth metals. The metal reacts directly with elemental carbon, nitrogen, boron, selenium, silicon, phosphorus, sulfur, and with halogens. It oxidizes rapidly when exposed to air. Cold water attacks lanthanum slowly, while hot water attacks it much more rapidly.
Applications
Uses of lanthanum:
Carbon lighting applications, especially by the motion picture industry for studio lighting and projection.
La2O3 improves the alkali resistance of glass, and is used in making special optical glasses, such as:
Hydrogen sponge alloys can contain lanthanum. These alloys are capable of storing up to 400 times their own volume of hydrogen gas in a reversible adsorption process.
Lanthanum was discovered in 1839 by Swedish chemist Carl Gustav Mosander, when he partially decomposed a sample of cerium nitrate by heating and treating the resulting salt with dilute nitric acid. From the resulting solution, he isolated a new rare earth he called lantana. Lanthanum was isolated in relatively pure form in 1923.
The word lanthanum comes from the Greek lanthanein, to lie hidden.
Biological Role
Lanthanum has no known biological role.
The element is not absorbed orally, and when injected its elimination is very slow. Lanthanum carbonate was approved as a medication (Fosrenol®, Shire Pharmaceuticals) to absorb excess phosphate in cases of end-stage renal failure. Some rare-earth chlorides, such as lanthanum chloride (LaCl3), are known to have anticoagulant properties.
Occurrence
Monazite (Ce, La, Th, Nd, Y)PO4, and bastnasite (Ce, La, Y)CO3F, are principal ores in which lanthanum occurs in percentages up to 25 percent and 38 percent.
See also category:Lanthanide minerals
Isotopes
Naturally occurring lanthanum is composed of one stable (139La) and one radioactive (138La) isotope, with the stable isotope, 139La, being the most abundant (99.91% natural abundance). 38 radioisotopes have been characterized with the most stable being 138La with a half-life of 1.05×1011 years, and 137La with a half-life of 60,000 years. All of the remaining radioactive isotopes have half-lives that are less than 24 hours and the majority of these have half lives that are less than 1 minute. This element also has 3 meta states.
The isotopes of lanthanum range in atomic weight from 117 u (117La) to 155 u (155La).
Precautions
Lanthanum has a low to moderate level of toxicity, and should be handled with care. In animals, the injection of lanthanum solutions produces glycaemia, low blood pressure, degeneration of the spleen and hepatic alterations.
"Lanthanum".
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