THERMAL-ANALYSIS OF SOME MIXED-METAL OXALATES

The mixed metal oxalates, FeCu(ox)2.3H2O, CoCu(ox)2.3H2O, and NiCu(ox) 2.3.5H2O, [ox = C2O4] have been prepared by coprecipitation from solut ion. The thermal behaviour of these compounds in nitrogen and in oxyge n has been examined using thermogravimetry (TG), thermomagnetometry (T M), differential scanning calorimetry (DSC) and evolved gas analysis ( EGA). The thermal behaviour of the mixed oxalates, MCu(OX)2.xH2O, diff ered from that of the individual metal oxalates, Cuox, Coox.2H2O, Niox .2H2O and Feox.2H2O. All three mixed oxalates, on heating in N2, first dehydrate and then decompose in two overlapping endothermic stages. B oth CO and CO2 were evolved in proportions which varied with the surro unding atmosphere, and from compound to compound, and with extent of r eaction of a given compound. The mixed oxalates, MCu(ox)2.xH2O, do not show the exothermic behaviour characteristic of Cuox, and reasons for this are discussed.