An investigation of decomposition of Trigonox 21S in Shellsol T has been carried out using the proposed algorithm. A series of calorimetry experiments were performed, where temperature and pressure of the system were monitored. The numerical code has been developed using an annealing optimisation algorithm to find chemical kinetics and the solubility of carbon dioxide in the reacting solutions. The overall decomposition reaction can be represented by a first-order reaction mechanism with a chemical reaction rate approximated by an Arrhenius type expression with a pre-exponential factor of 4.300 x 10(13) s(-1) and an activation energy 1.227 x 10(5) J/mol with heat of reaction 1.904 x 10(5) J/mol. Sensitivity analysis has been performed as well. It has been shown that the system is the most sensitive to the value of activation energy and logarithm of the pre-exponential factor. (c) 2007 Elsevier B.V. All rights reserved.