Nonisothermal kinetics with programmed temperature steps.

Data required for predicting the stability of an active principle in solution can be obtained by two kinetic methods. With the isothermal method, the degradation rate constants are determined at different temperatures, which are kept constant throughout the experiment. With the nonisothermal method, the temperature is increased with time. This paper describes a nonisothermal kinetic method in which the temperature is increased in consecutive equal steps. The results are compared with those obtained by the conventional isothermal method. The values for the activation energy are approximately the same by both methods. Although the technique of nonisothermal kinetics demands sophisticated equipment and high experimental accuracy, it provides a continuous picture over a wide temperature range.