Thorium Superoxide, Th₂O₇

Thorium Superoxide, Th₂O₇, is obtained in a hydrated form when ammonia is added to a mixture of thorium acetate or sulphate solution and hydrogen peroxide. This superoxide is rather unstable and easily loses some oxygen, so passing into more stable trioxide, ThO₃. By the action of dilute sulphuric acid on the superoxide, Th₂O₇, hydrogen peroxide is formed in solution, whilst concentrated sulphuric acid yields ozonised oxygen. The superoxide Th₂O₇ is formed by the action of hypochlorite as well as hydrogen peroxide on Th(OH)₄, and also by the electrolysis of an alkaline solution of sodium chloride in which thorium hydroxide, Th(OH)₄, is suspended. It is therefore regarded by Pissarjewski as a true superoxide, and not merely an addition compound of Th(OH)₄ and H₂O₂. Its formation from the nitrate is therefore thus represented:

Th(NO₃)₄ + 4HO₂H = Th(O₂H)₄ + 4HNO₃,

Th(O₂H)₄ being a salt of hydrogen peroxide, which is subsequently hydrolysed to Th(O₂H)₂(OH)₂ and Th(O₂H)(OH)₃, a mixture of which constitutes Th₂O₇.