Uranium trioxide

Uranium trioxide

Yellow- orange crystals

Fixed

7.30 g · cm -3

Risk

Template: Infobox chemical / molecular formula search is not possible

Uranium (VI ) oxide ( also uranium trioxide, UO3 ) is a chemical compound that forms yellow or orange crystals, depending on the modification and is one of the heavy metal oxides.

Production and representation

Uranium (VI ) oxide is prepared by heating of uranyl compounds such as uranyl nitrate hexahydrate in an oxygen atmosphere at 600 ° C.

It can (, VI V) oxide are shown with oxygen at high pressure by reaction of uranium, which arise depending on pressure and temperature, various modifications.

Properties

Physical Properties

Uranium ( VI) oxide is radioactive due to the uranium content. We know an amorphous and six different crystalline modifications, in which uranium is the coordination number 6 or 7 has.

• α - UO3 may amorphous uranium ( VI) oxide is obtained by heating to 500 ° C at an oxygen partial pressure of 40 bar as a beige crystalline powder. It has an orthorhombic structure (space group C2mm ).

• β - UO3 is obtained from α - UO3 at 550 ° C and an oxygen partial pressure of 40 bar as an orange or red powder. It is also formed by heating diuranate to 500 ° C in air. β - UO3 crystallizes in the monoclinic space group P21.

• γ - UO3 is formed by heating uranyl nitrate hexahydrate in air at 400-600 ° C as a yellow powder. It crystallizes in the tetragonal space group I41/amd. At 50 ° C it goes into an orthorhombic structure (space group Fddd ) on

• δ - UO3 is formed during dehydration of β - UO3 · H2O at 375 ° C in air as a deep red powder. The crystal structure is cubic (space group Pm3m )

• ε - UO3 is formed from U3O8 to NO2 at 250-375 ° C as a red powder.

• ζ - UO3 is a high-pressure modification, which is formed at 30 kbar and 1100 ° C. It crystallizes in the orthorhombic space group P212121

Freshly produced uranium ( VI) oxide from terrestrial natural uranium has a specific activity of 21050 Bq / g

Chemical Properties

Uranium ( VI) oxide is amphoteric. In acidic solutions it forms uranyl UO22 . In alkaline medium Oxouranate be formed. At 700-900 ° C it decomposes into Triuranium octoxide.

Use

The largest part is further processed into uranium dioxide, otherwise there is no important use.

Toxicology

The chemical toxicity of this metal oxide is much more dangerous than its radioactivity. So it must be taken especially precaution against poisoning.