Single-pellet moment technique which was initially proposed for the measurement of effective diffusivities in porous catalysts and adsorption rate and equilibrium constants was modified for the analysis of gas-solid reactions. In this technique dynamic version of the Wicke-Kallenbach single-pellet cell was used A pulse of a tracer gas was introduced into stream flowing over one end face of the pellet. In the modified pulse-double response procedure, experimental moments of the response peaks of both reactant and product Bases measured in both top and bottom outlet streams of the single-pellet reader wee used for the evaluation of intrapellet rate and equilibrium parameters. Application of the technique to the reaction of SO2 with activated soda indicated that the value of while modulus decreased from 6.74 to 0.33 by the increase of fractional conversion of Na2CO3 to Na2SO3 from zero to 0.63. In this range of conversion values a significant variation in pore structure and also a decrease of effective diffusivity of SO2 from 0.045 cm(2)/s to 0.025 cm(2)/s was observed. A cell model which considered the changes in pore length and radius with reaction extent and variations in product lays diffusion resistance was shown to be successfully used in the analysis of experimental observations. A review of single-pellet dynamic reader studies for catalytic and noncatalytic gas-solid reactions was also given.