Uranic anhydride

Uranyl-vanadates.—By adding uranic anhydride to fused potassium or sodium metavanadate, microscopic, rectangular, fluorescent plates of the compositions K(U02)V04 and Na(U02)V04 are obtained. These are probably derivatives of a relatively stable uranyl-... 

Uranium Trioxide, Uranic Oxide, Uranic Anhydride, or Uranyl Oxide, UO3, is obtained when uranic acid, ammonium diuranate, or ammonium uranyl carbonate is heated to a temperature not exceeding 300° Cd When uranyl nitrate is similarly heated the product always contains basic nitrate, but if this product is heated in a current of oxygen at 500° C. it yields pure uranium trioxide. ... 

The dihydrate is formed by evaporation at ordinary temperature of an ethereal solution of the hexahydrate which has been dried with calcium nitrate or by crystallisation of the hexahydrate from concentrated nitric acid solution. It yields small lustrous plates, thick and square, probably rhombic, and possessing a green fluorescence. It melts at 179-3° C. It is much more stable than the trihydrate, and can be kept in a vacuum desiccator with caustic alkali or i hosphorus pentoxide without any loss of water. It dissolves readily in ether. If the dihydrate is heated in a current of carbon dio.xide at 98° C. a product corresponding very nearly in composition to the nioiiohydrate, U03(N03)3.H20, is obtained at 160° C. under the same conditions the ankydi ffus salt, U02(N03)2, is obtained. The latter may also be obtained by passing a current of dry nitric anhydride over the tri-hydrate carefully heated at 170° to 180° C. It is a yellow amorphous powder, readily soluble in water with c -olution of heat. It reacts violently with ether. When heated to 200° C. it decomposes and leaves a mixture of uranic acid, UO3.H2O, and uranic anhydride. ... 

The two chief oxides of uranium are the basic uranous oxide UO2 and the acid anhydride UO3. Intermediate between these two is a well-defined green oxide of composition UgOg. Less certain is the existence of a pentoxide UgOj, and a tetroxide, uranium peroxide, UO, though well-defined derivatives of the latter, peruranates, are known. 

Uranium trioxide is slightly basic, but with the exception of uranium hexafluoride, the salts formed by interaction with acids still contain two-thirds of its oxygen in the form of the uranyl radical, compounds of the type UOjR g being produced. On the other hand, however, the oxide acts towards strong bases as an acid anhydride, similar to chromic anhydride, and produces stable uranates. In contact with water it readily forms uranic acid, U02(0H)2. ... 

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