The study of the thermal decomposition of V2(SO4)3, VOSO4 · 5 H2O, VO(CH3-(COO)2 and VOC2O4 · 2 H2O has been made in argon and hydrogen atmospheres and compared with that in air by following thermogravimetry and differential thermal analysis. The decomposition products are characterized by chemical analysis, IR, and X-ray powder diffraction methods. The results suggest that all the salts decompose to V2O5 in air and to V2O3 in hydrogen. In argon atmosphere, the sulphates decompose to V2O5 whereas the carboxylates decompose to V2O3. © 1981.