SELENIUM

(Lat.), n. n. Se2l-en(an)'i2-usm(u4m). From aeA^K>j, the moon. Fr., selenium. Ger., Selen. A non-metallic element discovered by Berzelius in 1817. It occurs in nature in combination with sulphur and with metals in many minerals. Ordinary, or soluble, s. is either a bright-red powder or a black micro-crystalline powder, soluble in carbon disulphide, and crystallizing from its solution in dark-red monoclinic crystals. When melted and quickly cooled it forms a dark-colored, translucent, vitreous, brittle substance. When melted, cooled to 210 C., and maintained at this temperature for some time, soluble s. is transformed into so-called metallic s., or insoluble s., a granular, crystalline ma , insoluble in carbon disulphide. S., when sublimed, gives off a dark-red vapor, which condenses into the so-called scarlet flowers of s. In composition s. is usually bivalent, replacing two atoms of hydrogen, but acts as a quadrivalent or sexvalent radicle. In the formation of its E, he; E2, ell; G, go; I, die; I2, in; N, in; N2, tank; [s. 470]