COMPARATIVE-STUDIES ON THE THERMAL-DECOMPOSITION OF M[M(C2O4)2].XH2O (X = 4 FOR M = MN(II), CO(II), ZN(II) X = 5 FOR M = NI(II) X = 6 FOR M = CD(II) AND X = 1 FOR M = SN(II))

The study reveals that the thermal decomposition of most of the complexes M[M(C2O4)2].xH2O (where x = 4 for M = Mn, Co or Zn; x = 5 for M = Ni; x = 6 for M = Cd; and x = 1 for M = Sn) gives the anhydrous compound which on exposure to humid atmosphere is rehydrated to the original form. In air, the metal oxides were formed directly as a solid decomposition product and in nitrogen metal oxides were formed through the formation of an intermediate mixture of metal or metal oxide and metal oxalate. The evolved CO(g) exerted some additional effects in the decomposition of oxalates and the fused metal oxides had a profound effect on the decomposition of the intermediate metal oxalates. The kinetic parameters for the dehydration and decomposition steps varied according to the atmosphere and different values were obtained for the same step depending on the method applied. Variations were observed in the values calculated from thermogravimetric and differential scanning calorimetric curves.