A comparative study of the isothermal and non-isothermal decompositions of malonic acid has been carried out using the gasometric technique at atmospheric pressure. Under isothermal conditions, the results indicate two different mechanisms. At lower operating temperatures the decomposition process is governed by first-order kinetics, while at higher ~temperatures it is controlled by the random nucleation Erofeev equation. Analysis of the non-isothermal TG curves proved the advantageous use of this technique. It provides quick and valid information about the the r~nal decomposition kinetics of malonic acid, both in the pure state and when catalysed by solid 12-molybdophosphoric acid and its bismuth salts. Via the applicability of a non-isothermal kihetic equation, it was demonstrated that the factor causing the enhancemen! effect of these catalysts is mainly electronic in nature.The kinetics of thermal decomposition of solids has attracted the interest of investigators under both isothermal and non-isothermal conditions. It has been reported [1,2] that the kinetic analysis of thermogravimetric data obtained under isothermal conditions is preferable, with the integral kinetic equationwhere ~ is the fraction of solid decomposed after time t, K is the constant rate, which is related with temperature by the Arrhenius equation

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