Lanthanum

Lanthanum (La) is a nonessential element. In its pure form, it is a rather soft, silvery-white metal, which tarnishes rapidly in air. Its atomic weight is 138.9055 and its atomic number is 57. Rare earth elements including La are relatively abundant in the Earth’s crust, but finding them where they can be economically mined and processed presents a challenge. China is presumed to be responsible for over 95% of the world’s mine production. The chemistry of La primarily concerns its formation of the ionic +3 oxidation state. Lanthanum oxide improves the alkali resistance of glass: it is used in making special optical glasses, such as infrared-absorbing glass, as well as camera and telescope lenses, because of the high refractive index and the low dispersion of rare earth glass. Small amounts of lanthanum added to steel improve its malleability.Microelement fertilizers with lanthanum as a main component have been used in Chinese plant production for about 30 years to improve yield and quality. In the general population the mean dietary intake of La and lanthanides is estimated to be below 150. μg, which is less than 5% of the estimated acceptable daily intake. Lanthanum in drinking water samples is reported to be...