The Polanyi-Dubinin equation was used to predict adsorption isotherms for eight organic vapors at 25℃ and for two organic vapors at 25℃

40℃ and 60℃ on activated carbon in this analysis. The theoretical affinity coefficient

β

was calculated by three methods(molar volume

molecular parachor and electronic polarization) based on nonpolar and polar reference vapors. The corresponding experimental isotherm data were measured by gravimetric method. A comparison between calculated and measured isotherm data showed that ( 1 ) for optimum isotherm prediction

the reference vapor should be similar in polarity to the vapor whose adsorption is to be predicted

( 2 ) after choosing an appropriate reference vapor

there is essentially no difference in the accuracy of the isotherm predictions by the three methods

( 3 )the molar volume mth-od is more applicable for predicting isotherms at different temperatures.