(L. radius, ray) Radium was discovered in 1898 by Mme. Curie in the pitchblende oruraninite of North Bohemia, where it occurs. There is about 1 g of radium in 7 tons ofpitchblende. The element was isolated in 1911 by Mme. Curie and Debierne by; theelectrolysis of a solution of pure radium chloride, employing a mercury cathode; ondistillation in an atmosphere of hydrogen this amalgam yielded the pure metal.

Originally, radium was obtained from the rich pitchblende ore found in Joachimsthal,Bohemia. The carnotite sands of Colorado furnish some radium, but richer ores are found inthe Republic of Zaire and the Great Lake region of Canada. Radium is present in alluranium minerals, and could be extracted, if desired, from the extensive wastes of uraniumprocessing. Large uranium deposits are located in Ontario, New Mexico, Utah, Australia,and elsewhere.