Adsorption thermodynamic functions and the mobility of SO₂ on Aerosil

A study of the adsorption and thermodynamic functions of sulfur dioxide on Aerosil has been made, leading to some conclusions about the mobility of the SO₂ molecule. The differential and integral enthalpies and entropies of adsorption, together with a statistical mechanical interpretation of the system, are discussed. Particularly, the statistical mechanical calculation of the integral entropy of adsorption allows a comparison to be made between the experimental results for the SO₂-Aerosil system and those obtained for adsorption in two limiting cases: an immobile or localized model that can be associated with chemisorption, and a mobile film model that can be related to physisorption. The results confirm a weak gas-solid interaction with a highly mobile adsorbed phase.