Following previous work on the measurement of meaningful activation energies and the application of Constant Rate Thermal Analysis (CRTA) to the determination of kinetic parameters [1,2], here we further examine sources of error in determining activation energies and go on to consider the form of the alpha function and the value of A. Using theoretical arguments based on transition state theory, we conclude that allowing significant pressures of product gas to appear in the reaction environment will lead to very high values for apparent activation energies. We note that, although this is observed in practice for calcium carbonate, it in no way invalidates the application of the Arrhenius equation to solid state decomposition reactions, provided care is taken to avoid this type of distortion of experimental results. We attempt to determine the alpha function for the decomposition of calcium carbonate using data gathered from a variety of different types of temperature programme and reaction conditions. We find that the apparent alpha function depends on the method adopted and the experimental conditions used. We propose an explanation of why this occurs and tentatively introduce a new way of looking at the development of a reaction interface for this type of reaction. We review the literature and conclude that, while significant variations for the activation energy for the decomposition of calcium carbonate exist, a critical appraisal leads to good agreement amongst values that follow good experimental practice and reliable methods of data reduction. The apparent divergence of results can be explained in the light of the theoretical arguments advanced and the easily understood sourc-es of experimental error. IntroductionThis article is a companion of two previous articles [1, 2] and they are best read in chronological order. Some knowledge of these articles and the kinetic conventions used therein is assumed in the text. In these previous articles we recalled an observation made in a comprehensive review of the We then went on to consider the case of the thermal decomposition of calcium carbonate in some detail. We confined our attention to the activation energy and presented results that suggested the widely dispersed values for this parameter reported in the literature could be explained, in large measure, by poor choice of experimental conditions and/or the method chosen for the subsequent analysis of experimental data to extract kinetic information. In particular, the results suggested that on both theoretical and practical grounds the method known as Constant Rate Thermal Analysis (CRTA) has significant advantages for studying the kinetics of solid state decomposition reactions. The potential of this technique was explored in some detail and the Reduced Temperature Plot as a method for determining the alpha function for a reaction, was introduced.In this article we present a theoretical treatment of the kinetics of solid state decomposition reactions that investigates the effect of the partial pressure of the...

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