Molecular sieve effects of powders towards dyes. Measurement of porosity by dye adsorption

Abstract

p-Nitrophenol (PNP) in water or in benzene solution, and several dyes, have been used to measure the apparent specific surface of porous charcoals, silicas and alumina by adsorption. The results reveal a relation between the apparent surface and pore size distribution. The method measures the actual surface accessible through pores of given minimum radius, rather than the pore volume, which is the parameter measured by, e.g., benzene desorption or mercury porosimetry. Nevertheless, when allowance is made for the probable aggregate size of the adsorbed dye, there is reasonable agreement between results by the present method, and these other two methods. The present methods offer a simple means of determining pore size and area distribution in the transitional pore range, which is the range of most interest in treatments involving liquids.