1. During the adsorption of nitrogen oxides by the ASM grade silica gel, the increase in relative saturation is accompanied by a rapid fall in the total mass transfer coefficient caused by the increased diffusion resistance of the adsorbate in the pores of the adsorbent. 2. By criterial analysis of the experimental data and considering the coefficient of mass transfer through the gas film surrounding a porous particle, it is possible to generalize the studies on adsorption, solution, sublimation, and drying in fluidized systems, as well as the results of experiments on mass transfer from single drops and particles. 3. A criterial equation has been found, which defines the coefficients of mass transfer between particles and gas (liquid) in the diffusion region. 4. A coefficient of adsorbate distributionψ has been proposed for quantitative evaluation of the adsorbate per unit mass of the bed and for uniform distribution of the gaseous phase; the values of this coefficient have been determined for the conditions of our experiments and those of [1].