3904. Europium

Nomenclature

CAS number: 7440-53-1

Description and references

Eu; at. wt 151.964; at. no. 63; valences 2, 3. A lanthanide; belongs to cerium group of rare earth metals. Naturally occurring isotopes (mass numbers): 151 (47.8%); 153 (52.2%); known artificial radioactive isotopes: 138-150; 152; 154-160. Abundance in earth's crust: 1.06-2.1 ppm. Commercially important sources are the rare earth minerals monazite and bastnaesite; also found in gadolinite. Has been detected spectroscopically in the sun and in certain stars. Discovered and prepd as the oxide: Demarcay, Compt. Rend. 122, 728 (1896); 130, 1019, 1469 (1900); 132, 1484 (1901). Separation: Spedding et al., J. Am. Chem. Soc. 76, 2557 (1954); by paper chromatography: Lederer, Nature 176, 462 (1953). Toxicity study: Haley, J. Pharm. Sci. 54, 663 (1965). Reviews of prepn, properties and compds: The Rare Earths, F. H. Spedding, A. H. Daane, Eds. (Krieger, Huntington, N.Y., 1971, reprint of 1961 ed.) 641 pp; S. P. Sinha, Europium (Springer, New York, 1967) 164 pp; Hulet, Bode, “Separation Chemistry of the Lanthanides and Transplutonium Actinides” in MTP Int. Rev. Sci.: Inorg. Chem., Ser. One vol. 7, K. W. Bagnall, Ed. (University Park Press, Baltimore, 1972) pp 1-45; Moeller, “The Lanthanides” in Comprehensive Inorganic Chemistry vol. 4, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 1-101; F. H. Spedding in Kirk-Othmer Encyclopedia of Chemical Technology vol. 19 (John Wiley & Sons, New York, 3rd ed., 1982) pp 833-854; Chemistry of the Elements, N. N. Greenwood, A. Earnshaw, Eds. (Pergamon Press, New York, 1984) pp 1423-1449. Brief review of properties: G. T. Seaborg, Radiochim. Acta 61, 115-122 (1993).

Properties

Body-centered cubic crystal lattice; d 5.244; mp 826°. bp 1429°. Heat of fusion: 9.221 kJ/mol. Heat of sublimation (25°): 144.7 kJ/mol. Sol in liquid ammonia. Shows two reduction potentials -0.710 and -2.510 v. (referred to a normal calomel electrode): Noddack, Brukl, Angew. Chem. 50, 362 (1937); gives two definite series of salts, in one the metal is divalent, and in the other it is trivalent.

Derivative

Sesquioxide.

Nomenclature

Europia.
Eu2O3; mol wt 351.93.
Eu 86.36%, O 13.64%.

Properties

Pink powder, d 7.42, prepd by heating the hydroxide, nitrate, oxalate or sulfate at 1600°. The oxide of the divalent metal is prepd by reduction of the sesquioxide at elevated temp.

Derivative

Hydroxide.
Eu(OH)3; mol wt 202.99.
Eu 74.86%, O 23.65%, H 1.49%.

Properties

Prepd by adding ammonia or an alkali hydroxide to a soln of an europic salt.

Derivative

Europic chloride.
EuCl3; mol wt 258.32.
Eu 58.83%, Cl 41.17%.

Properties

Greenish-yellow needles; mp 623° in nitrogen (in a closed tube), d35 4.471, prepd by passing sulfur chloride over the heated oxide at 200-500°. LD50 of trichloride in mice: 550 mg/kg i.p.; 5 g/kg orally (Haley).

Derivative

Europous chloride.
EuCl2; mol wt 222.87.
Eu 68.19%, Cl 31.81%.

Properties

Prepd by reduction of EuCl3 with hydrogen at 600°. White amorphous powder, sol in water.

Derivative

Europic sulfate.
Eu2(SO4)3; mol wt 592.12.
Eu 51.33%, S 16.25%, O 32.42%.

Properties

Octahydrate, a pinkish cryst solid, prepd by dissolving the oxide in sulfuric acid. Soly in water: 2.56 parts per 100 parts at 20°, 1.93 parts per 100 parts at 40°. On heating at 375° yields the anhydr sulfate.

Derivative

Europic nitrate.
Eu(NO3)3; mol wt 337.98.
Eu 44.96%, N 12.43%, O 42.60%.

Properties

Hexahydrate, mp 85° in its water of crystallization (sealed tube). LD50 in rats (mg/kg): 210 i.p.; >5000 orally (Haley).

Derivative

Europous sulfate.
EuSO4; mol wt 248.03.
Eu 61.27%, S 12.93%, O 25.80%.

Properties

Colorless crystals. Insol in water and in dil acids. Prepd by electrolytic reduction of europic salts.

Use

The salts in cathode ray tube coatings for color television receivers. Eu has a very high cross-section for the capture of thermal neutrons which is of value in the construction of electric atomic power stations. Organic derivs as shift reagents in NMR spectroscopy: C. C. Hinckley, J. Am. Chem. Soc. 91, 5160 (1969); R. E. Sievers, Nuclear Magnetic Resonance Shift Reagents (Academic Press, New York, 1973).