The flow rates of the vapors of benzene, ethyl chloride, diethyl ether, methanol, and water through activated carbon rods have been found to exceed, considerably, flow rates calculated by classical equations. The excess flow rates show maxima in widely different relative pressure regions and are ascribed to flow of adsorbed material. An empirical equation is presented which correlates the observed flow rates with relevant adsorption isotherms. Classical equations of flow through elliptical and rectangular pipes are discussed with reference to flow through fine-grained porous materials. It is shown that equations of the Adzumi type are roughly valid as applied to fine-grained porous bodies, but that without a knowledge of the frequency distributions of pore sizes and shapes, flow data cannot be related to pore dimensions in any literal sense. End effects are discussed.
