SOME THERMODYNAMIC PROPERTIES OF HYDROCARBONS ADSORBED ON RUTILE

Differential thermodynamic properties of methane, ethane, propane, and n-butane adsorbed on rutile have been determined from isotherms over appreciable temperature ranges. Ordinary experimental techniques failed to yield reliable data in low temperature and surface coverage regions, but essentially simple modifications of these resulted in accurate thermodynamic values. For methane, the results compared well with similar ones computed by Pace, Heric, and Dennis from data obtained by means of calorimetry. Maximum error in isosteric heats of adsorption was 60 cal. mole −1 ; in differential molar entropies 0.8 cal. mole −1 degree −1 . The thermodynamic properties of methane and ethane are similar but there is a departure in the set pattern for propane. A large change was observed in the heat of adsorption of propane, near 185° K. and surface coverages lower than 0.6 of the monolayer. A phase transition is suggested to account for this occurrence.