Compounds which undergo strongly exothermic decompositions (some molybdenum peroxo complexes in this study) were investigated as possible temperature calibrants in thermogravimetry (TG). Onset temperatures of these exothermic reactions were determined using a differential scanning calorimeter (DSC) which had been calibrated on the melting points of standard materials. These onset temperatures in the DSC were compared with the onset temperatures of the explosive reactions of small samples in the TG. Details of the preparation of the complexes used are given, but it is expected that suggestions for other suitable substances will be forthcoming.