Didymium

Didymium is a very rare metal found in the minerals Cerite, Allanite, &c. Its symbol is Di, its atomic weight 142, and its specific gravity 6.5. It is found associated with Cerium and Lanthanum, and as the salts of the three metals have closely similar properties, their separation is very difficult. The salts of didymium are generally soluble and rose-coloured. The hydrated oxide is a gelatinous precipitate resembling alumina. Its compounds have nothing specially characteristic in their properties except the absorption bands in the spectrum. The metal, which has an iron-gray colour, with a yellowish tinge, tarnishes in the air, and burns brilliantly when held in a flame.