GADOLINIUM is a metallic element belonging to the rare earth group (symbol Gd, atomic number 64, atomic weight 157-3). The early history of this element is in a rather confused state. Marignac in 1880 obtained a new earth in an impure condition and termed it and then in 1886 he gave it the name it now bears. Pure gadolinium salts were obtained by Demarcay in 1900. It occurs in many minerals, some varieties of Norwegian ytterspar being quite rich sources ; other common sources are gadolinite, samarskite, monazite. It is best separated from other members of the group by first crystallizing the double magnesium nitrates. The most soluble portion of these nitrates is then con verted to the bromates and further fractionally crystallized. Gadolinium gives a white oxide and colourless salts, the simple nitrate being the least soluble of the rare-earth series; in solution these give absorption bands in the ultra violet. While gadolinium is far from common, it is not as rare as is generally believed. (See RARE EARTHS.) (C. J.)