La lenoblite, nouvel oxyde hydraté de vanadium (IV)

Lenoblite, which occurs associated with duttonite VO (OH)₂ in the uranium deposit at Mounana, Gabon, is distinguishable from the others oxides of V⁴⁺ by its powder pattern ; the principal spacings are 7.46 ms, 4.59 vvs, 3.722 vs, 2.528 Å s. The chemical analysis is Fe₂O₃ 0.35 %, Al₂O₃ 1.16%, V₂O₄ 69.45 %, V₂O₅ 10.27 %, H₂O 17.93 %, insol. 0.50 %, total 99.66 % which leads to the formula V₂O₄.₁₂ . 2.09 H₂O but since an oxidation study showed the formation of an amorphous hydrated phase, the formula of unaltered lenoblite is very probably V₂O₄.2H₂O. The thermal behaviours of lenoblite, of duttonite and of synthetic V₂O₄.2H₂O are very similar. Differential thermal analysis curves show the following phenomena : dehydration, oxidation of V⁴⁺ to V⁵⁺, crystallization, then fusion of V₂O₅. The parameters of the associated duttonite are a = 8.77 Å, b = 3.94 Å, c = 5.93 Å et p = 90° 20', space group I2/c.