Uranous Hydroxide

The addition of alkali to a solution of a uranous salt produces a reddish-brown gelatinous precipitate, which darkens in colour on boiling the solution. If dried in vacuo it becomes black and has the composition UO₂.H₂O. This rapidly oxidises in the air and readily dissolves in dilute acids, forming uranous salts. It acts upon a neutral solution of silver nitrate, first precipitating silver oxide and forming a green solution which, however, soon turns yellow, and the oxide is reduced to metallic silver as the uranyl salt forms in solution, thus:

1. 4AgNO₃ + UO₂ = 2Ag₂O + U(NO₃)₄,
2. U(NO₃)₄ + 2Ag₂O = UO₂(NO₃)₂ + 2AgNO₃ + 2Ag.

According to Aloy, a black crystalline hydrate, of composition UO₂.2H₂O, is obtained when crystallised uranous sulphate is treated with hot potassium or sodium hydroxide solution. The product, when thoroughly washed, remains stable in air for several days. It dissolves in dilute acids, yielding uranous salts. On heating, it is completely converted to the green oxide.