Various lanthanides are used in the pyrophoric alloy, misch metal. Containing 50% cerium, 25% lanthanum, and smaller amounts of elements such as praseodymium and samarium, misch metal is employed in cigarette lighter flints, where its readiness to spark makes it ideal.
Lanthanides are also used in special glasses, where they filter certain kinds of light. Praseodymium and neodymium, for example, are used in glass for welders' and glassmakers' goggles, serving to absorb the yellow light that would be damaging to the eyes.
Several members of the series, including samarium, europium and gadolinium, are used in control rods in nuclear reactors, because of their ability to absorb the neutrons which perpetuate chain reactions. Hafnium is used in this capacity in nuclear submarines.
Further uses include as phosphors in colour television tubes. Europium is employed in red phosphors, terbium in green. Mixtures of the metals' oxides are used for catalytic purposes in petroleum cracking.
