Thermal dehydration and structural models of two new vanadyl sulfate hydrates

Abstract The preparation of a new modification of vanadyl sulfate trihydrate, VOSO 4 · 3H 2 O, is described. In the course of its thermal dehydration, another new phase, VOSO 4 · 2H 2 O, is observed as an intermediate. Crystal data for the two compounds are: VOSO 4 · 3H 2 O, orthorhombic, a = 8.980 ± 0.006, b = 9.026 ± 0.009, c = 7.776 ± 0.003 A, space group P 2 1 2 1 2; VOSO 4 · 2H 2 O, monoclinic, a = 8.913 ± 0.027, b = 8.93 ± 0.09, c = 7.80 ± 0.06 A, β = 92.4 ± 0.6°. From the topotaxy of the dehydration reaction, structural models for the two phases are deduced. They consist essentially of VOSO 4 layers similar to those in α-VOSO 4 and interlayer water.