Quantitative Characterization of the Peak Aspect

The fact that the peak appears sharp and narrow with a high maximum heat release rate may be expressed in a quantitative way. The first idea is to measure the peak height and width and to use a ratio in order to determine if the reaction is autocatalytic or not. Even if this method looks simple, its drawback is that only a few points are used to describe the peak. Thus, the statistic significance of such an evaluation is poor. 

This method was validated with over 100 substances and compared with the results of the classical study by isothermal experiments. For apparent activation energies above a level of 220 kj mol 1, 100% of the samples showed an autocatalytic character in isothermal experiments. This method can be used as a screen to distinguish clearly autocatalytic reactions from others that should be studied by isothermal experiments. This reduces the number of isothermal experiments required. 

Temperature-programmed DSC, or DTA measurements, can only suggest the autocatalytic nature of the decomposition. Neither the influence of the thermal history and contamination can be detected by them, nor can the kinetic parameters be determined from a single experiment. 

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