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
Polonium methylated in living things to create organometallic compounds. Studies investigating the metabolism of polonium-210 in rats have shown that only 0.002 to 0.009% of polonium-210 ingested is excreted as volatile polonium-210. The median lethal dose (LD) for acute radiation exposure is about 4.5 Sv. The committed effective dose equivalent Po is 0.51 µSv/Bq if ingested, and 2.5 µSv/Bq if inhaled. So a fatal 4.5 Sv dose can be caused by ingesting , about 50 nanograms (ng), or inhaling , about 10 ng. One gram of Po could thus in theory poison 20 million people of whom 10 million would die.