Polonium initiator was classified until the 1960s. The Atomic Energy Commission and the Manhattan Project funded human experiments using polonium on five people at the University of Rochester between 1943 and 1947. The people were administered between of polonium to study its excretion. Polonium is a very rare element in nature because of the short half-life of all its isotopes. Po, Po, and Po appear in the decay chain of U; thus polonium can be found in uranium ores at about 0.1 mg per metric ton (1 part in 10), which is approximately 0.2% of the abundance of radium. The amounts
Polonium trioxide that polonium trioxide may be formed by heating polonium dioxide and chromium trioxide together in air. It is very difficult to oxidize polonium beyond Po(IV); for example, the only hexahalide of polonium is the hexafluoride, PoF, and fluorine is already the most electronegative element (though polonium hexaiodide was once reportedly formed in the vapour phase, it immediately decomposed). However, the difficulty in obtaining polonium trioxide and polonates (containing the anion, analogous to sulfate, selenate, and tellurate) by direct oxidation of Po(IV) compounds may be due to the fact that polonium-210, while the most easily available isotope of polonium, is strongly