A MODIFICATION OF THE DUBININ ISOTHERM

The Dubinin isotherm expression is modified to include the proper Henry's law limit. The resulting isotherm has the flexibility of the Dubinin form, with a minimum of parameters, while being thermodynamically consistent. Comparisons are made to two multiparameter expansions, the virial and a modified vapor pressure based expansion. Data for chlorofluorocarbon refrigerants and light hydrocarbons on activated carbons and for methane on zeolites, covering wide ranges of concentration and temperature, are well correlated by the modified isotherm with parameters that are independent of temperature.