It has been found that cobalt(II, III) oxide, Co 3O 4, lowers the thermal decomposition temperature of Na 2S 2O 8 and K 2S 2O 8 by about 25°C by catalysis, and it therefore acts as a P-type semiconductor at high temperature and atmospheric (air) pressure. Also, this oxide reacts at high temperature with sodium or potassium pyrosulfates to form thermally stable sodium cobalt disulfate, Na 2Co(SO 4) 2 and potassium cobalt trisulfate, K 2Co 2(SO 4) 3, respectively. Binary systems, consisting of a 1 : 3 mole ratio (oxide : persulfate), are established as representing the solid state stoichiometric reaction. X-Ray diffractometry is employed to identify intermediate and final reaction products in general. All calculations are based on data obtained from TG, DTG and DTA curves.