Polonium Oxides and Sulfides

The treatment of polonium(lV) with nitric acid/potassium permanganate under reflux yields a sludge of manganese dioxide which contains all the polonium originally present the valency state is uncertain. Polonium (IV) in weighable amounts is not oxidized by persulfate, ceric salts or chlorine in alkaline solution (12), although trace scale work indicates that both ceric salts and dichromate do oxidize polonium to polonium(VI) (94). 

Fusion of polonium dioxide with a potassium chlorate/hydroxide mixture gives a bluish solid (colorless when hot) which is more soluble in water than the corresponding polonite (Po032 ) this presumably contains some potassium polonate. The trioxide may possibly be formed by strongly heating polonium dioxide and chromium trioxide in air (12). 

The radius of the Po4+ ion calculated from the X-ray data is 1.02 A (93) or 1.04 A (5) the ratio of the ionic radii Po4+/02 is thus about 0.73, the lower limit of stability for cubic coordination, explaining the existence of the two modifications (93). 

Fusion of polonium dioxide with potassium hydroxide in air, or with potassium nitrate, gives a colorless melt the solubility of the polonium after this treatment corresponds with the solubility data for potassium polonite (12). 

The black monoxide appears to be formed by the spontaneous decomposition of polonium sulfotrioxide and selenotrioxide (10). The corresponding hydroxide (or hydrated oxide) is obtained as a dark brown precipitate when alkali is added to a freshly prepared solution of bipositive polonium (6). Both are rapidly oxidized to polonium(IV) in air or in contact with water. 

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