A new procedure for the prediction of the isothermal behaviour of the solid-gas system from non-isothermal data is suggested.
It bypasses the use of various approximations of the temperature integral that ground the integral methods of prediction.
The procedure was checked for: (1) simulated data corresponding to a first order reaction; (2) experimental data obtained
in the isothermal and non-isothermal decompositions of ammonium perchlorate. For the simulated data, a very good agreement
between calculated isotherms and those evaluated by means of the suggested procedure was obtained. A satisfactory agreement
(errors in time evaluation corresponding to a given degradation lower than 18%, for 0.10a0.37 and lower than 10% for 0.37a0.70)
was obtained for the experimental data corresponding to the decomposition of ammonium perchlorate. In this last case, the
mentioned differences between experimental and calculated data can be due both to the inherent errors in the evaluation of
the decomposition isotherms and to the dependence of the activation energy on the conversion degree.