Appearance and Characteristics
Harmful effects:
Lanthanum and its compounds are considered to be moderately toxic.
Characteristics:
Lanthanum is a silvery-white soft metal, which can be cut with a knife. It is ductile, malleable and exposed surfaces tarnish rapidly in air forming the oxide. Lanthanum reacts with water to form lanthanum hydroxide plus hydrogen gas. Lanthanum is chemically reactive and forms compounds with carbon, nitrogen, boron, selenium, silicon, phosphorus, sulfur, and with the halogens. Lanthanum usually exists as a trivalent ion, La3+, in its compounds.
Uses of Lanthanum
Lanthanum is used in large quantities in nickel metal hydride (NiMH) rechargeable batteries for hybrid automobiles. The negative electrode (cathode) in NiMH batteries is a mixture of metal hydrides – one of which is typically lanthanum hydride. The active material at the cathode is hydrogen, which is stored in the metal hydride structure. The metal hydride can, depending on its composition, hold between 1% and 7% hydrogen by weight.A Toyota Prius battery requires about 10 kg of lanthanum.
Lanthanum is used as a petroleum cracking catalyst, catalyzing the splitting of long chain hydrocarbons into shorter chained species. Lanthanum is used as an additive to make nodular cast iron and as an additive in steel. Flame lighter flints use misch metal (a rare earth alloy) containing lanthanum to produce sparks by friction. Lanthanum is used in hydrogen sponge alloys, which take up to 400 times their own volume of hydrogen gas. Lanthanum is also used to make night vision goggles (infrared-absorbing glass). High quality camera and telescope lenses contain lanthanum oxide (La2O3) making use of its high refractive index and low dispersion. Lanthanum carbonate is used to reduce blood levels of phosphate in patients with kidney disease. Lanthanum compounds are also used in some pool products to reduce the level of phosphate nutrients that algae feed on.