The thermal decomposition of transition metal sulphates was studied by thermogravimetry in static air. The TG, DTG and DTA curves were obtained using a Hungarian MOM C-derivatograph. Kinetic analysis of experimental TG-curves was carried out by applying the Coats and Redfern's equation. The thermodynamic functions of transient states were calculated from the Eyring equation. The thermal decomposition of investigated sulphates can be described by kinetic equation d alpha/dt = A.exp(-(E/RT)).(1-alpha)(n). The reaction order for all investigated sulphates is at short range 2/3. The thermal stability of sulphates increased with radius of the cation. The dependence of free enthalpy of activation complexes on decomposition temperature and radius of cation is rectilinear.