Prasannan et al. (1985, Chem. Engng Sci. 40, 1251-1261) developed a mathematical model to account for the effect of inerts on gas-solid reactions. The model is experimentally verified in this paper. A reaction system involving capture of CO2 by freshly prepared lime pellets was chosen and varying amounts of inert particles were added to the reactive particles to study the effect of this addition on the progress of the reaction. These results can be of great significance in achieving better solids utilization in many industrial systems, particularly where expensive solid sorbents are used for gas removal purposes. © 1987.