Dalvi and Suresh (AIChE J. 2011, 57, 1329-1338) proposed a model for the kinetics of a reaction between two particulate solids A and B, where B is the diffusing component, in terms of the average number of contact points N-AB between the two types of particles. In the present work, the applicability and validity of the model is studied, taking the formation of tricalcium aluminate from its immediate precursors as a candidate reaction. Partial analytical solutions to the Dalvi-Suresh model have been derived, and a simple parameter-estimation methodology has been developed. The data clearly show an influence of N-AB, and use of the Ginstling-Brounshtein model (Appl. Chein. USSR 1950, 23, 1327-1338) for parameter estimation leads to diffusivity values that depend on N-AB in a systematic way. Parameters estimated using the Dalvi-Suresh model, on the other hand, show only a random scatter and also show reasonable agreement with the values of diffusivity of Ca in oxides.