Marie Curie doubt, the Curies sought to isolate polonium and radium in pure form. Pitchblende is a complex mineral; the chemical separation of its constituents was an arduous task. The discovery of polonium had been relatively easy; chemically it resembles the element bismuth, and polonium was the only bismuth-like substance in the ore. Radium, however, was more elusive; it is closely related chemically to barium, and pitchblende contains both elements. By 1898 the Curies had obtained traces of radium, but appreciable quantities, uncontaminated with barium, were still beyond reach. The Curies undertook the arduous task of separating out radium salt by differential
The Apocalypse Element The Apocalypse Element The Apocalypse Element is a Big Finish Productions audio drama based on the long-running British science fiction television series "Doctor Who". It forms the second serial in the Dalek Empire arc, following on from events in "The Genocide Machine". The arc continues in "The Mutant Phase" and concludes in "The Time of the Daleks". At a conference on Archetryx between major temporal powers, the Sixth Doctor and Evelyn discover that Romana has been missing for twenty years and that the Daleks' newest weapon — the Apocalypse Element — threatens not only the Time Lords but the entire