Triuranium octoxide

Triuranium octoxide

Dark black - green solid

Fixed

8.38 g · cm -3

1150 ° C.

Insoluble in water

Risk

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Uranium (V, VI ) oxide ( also Triuranium octoxide, U3O8 ) is a chemical compound of uranium and is one of the oxides. It occurs in several modifications. Pitchblende contains no uranium (V, VI ) oxide, but uranium (IV ) oxide and supplemental oxygen.

Production and representation

Uranium (V, VI ) oxide formed during the heating of uranium ( VI) oxide at 700-900 ° C by oxygen delivery or of uranium (IV ) oxide by oxygen uptake. Just as it is formed during the heating of other uranium oxides to similar temperatures in air.

Properties

Physical Properties

Uranium (V, VI) oxide forms a plurality of modifications. In pure uranium (V, VI ) oxide at room temperature, the orthorhombic α - structure with space group C2mm and the lattice parameters a = 671 pm, b = 1196 pm and c = 414 pm thermodynamically stable. It is higher than 210 ° C in a hexagonal shape reversible (A = 681 pm, c = 414 pm, space group P62m ) on. Metastable at room temperature is orthorhombic β - structure with space group Cmcm and lattice parameters a = 707 pm, b = 1145 pm and c = 830 pm, which are formed by heating α - U3O8 at 1350 ° C in air and slow cooling can. In addition, a cubic, stable only at high pressure, stoichiometric modification is known.

Uranium (V, VI) oxide is dependent on the oxygen content of conductive, at room temperature, the electrical conductivity is at exactly stoichiometric uranium ( V, VI ) oxide, about 100 Ω -1 · m -1. The compound is a semiconductor of the n-type.

Freshly produced uranium (V, VI ) oxide from terrestrial natural uranium has a specific activity of 21450 Bq / g

Chemical Properties

Triuranium octoxide readily dissolves in oxidizing acids to form uranyl ions. In the reaction with hydrogen chloride at 700 ° C produced uranyl chloride.

By reaction with hydrogen at 700 ° C or carbon dioxide at 350 ° C, it is non-stoichiometric multiple intermediates for uranium ( IV) oxide is reduced.

Use

Since uranium (V, VI) oxide is formed from all of the uranium oxides at the same temperatures, it is used for gravimetric determination of the uranium content of such ores, used.