The effect of pre-heating on the kinetics of the thermal decomposition of pure and chloride and phosphate doped sodium oxalate has been studied, as a function of the time of pre-heating, at a temperatures of 783 K under isothermal conditions by thermogravimetry (TG). The model fitting analysis of the TG data shows that no single kinetic model describes the whole alpha versus t curve with a single rate constant throughout the decomposition reaction; Prout-Tompkins model best describes the acceleratory stage of the decomposition while the decay region is best fitted with the contracting cylinder model. The rates of both stages were decreased by pre-heating for 24-36 h and then remained constant. Pre-heating of sodium oxalate resulted in a significant decrease in the rate of thermal decomposition and the general nature of the effects of dopants remains unaffected in both stages of the thermal decomposition reaction. (c) 2012 Elsevier B.V. All rights reserved.