HOLMIUM, a metallic element, belonging to the rare-earth group, was discovered by Soret in 5878 and independently by Cleve in 1879. In 1912 the oxide was obtained in an almost pure form by Holmberg. Holmium occurs along with erbium, etc., in the minerals gadolinite, euxenite, xenotime, samarskite. It has the symbol, Ho, atomic number 67, and atomic weight 163.5. It is best separated by the crystallisation of the bromates and is thereby obtained mixed with yttrium, which may be removed by the fractional crystallisation of the double sodium sulphates in a vacuum at 25*-30° C. Holmium oxide is yellowish, soluble in many acids to form salts possessing an orange-yellow colour and of a high magnetic susceptibility. Solutions show a strong charac teristic absorption spectrum. See RARE EARTHS. (C. J.)