In this paper the thermal atabilities of 25 oxalato ooordination compounds have been studies mainly by gas ohromatography.Information whioh oan not be obtained from TG or DTA has been obtained by this method.The prinoipal findings may be summarized as follows: 1.When the thermal decomposition of the oxalato oomplexea of various metals was carried out in helium, the oryatalization and the coordination water were expelled.Thermal decomposition in hydrogen gave additional water as a result of the reduction of CO and CO₂ as well as of the metal oxide (Fig.8).The temperatures of dehydration of MC₂O₄·2H₂O(M=Mn, Ni, Fe, Co, Zn eto.) depended on the nature of the nations.An empirical equation giving relationship between the peak value of decomposition temperature and the ionic potential of the cation has been proposed.