Adsorbents possess two fundamental properties One property is the maximum adsorption capacity, which is determined from equilibrium adsorption isotherm. The other property is the adsorption rate constant, derivable from adsorption kinetics. Experimental data on the physical adsorption of water vapour by chromatographic silica gel, at different relative vapour pressures, were used to calculate values for the kinetic adsorption capacity and adsorption rate constant at room temperature. Various types of diffusivities were determined through equations derived by Fick. Total pore volume (0.58 1 cc gel) and specific surface area (744 m 2 g-l) were found by Gurvitsch rule and Kieselve’s equation respectively. An average pore radius (hydraulic) is 7.8 x 10-8 cm as obtained by a new method suggesting shapeless pore model. The study of these quantities provides a strong basis for evaluating surface properties of adsorbent.