Radium seventh of a gram of radium. One kilogram of the Earth's crust contains about 900 picograms of radium, and one liter of sea water contains about 89 femtograms of radium. Radium was discovered by Marie Sklodowska-Curie and her husband Pierre Curie on 21 December 1898, in a uraninite (pitchblende) sample. While studying the mineral earlier, the Curies removed uranium from it and found that the remaining material was still radioactive. They separated out an element similar to bismuth from pitchblende in July 1898, that turned out to be polonium. They then separated out a radioactive mixture consisting mostly of two
Polonium coolant. The longer-lived isotopes of polonium, Po and Po, can be formed by proton or deuteron bombardment of bismuth using a cyclotron. Other more neutron-rich and more unstable isotopes can be formed by the irradiation of platinum with carbon nuclei. Polonium-based sources of alpha particles were produced in the former Soviet Union. Such sources were applied for measuring the thickness of industrial coatings via attenuation of alpha radiation. Because of intense alpha radiation, a one-gram sample of Po will spontaneously heat up to above generating about 140 watts of power. Therefore, Po is used as an atomic heat source to