Comment on "Dynamic ion association in aqueous solutions of sulfate" [J. Chem. Phys. 123, 034508 (2005)

The "dynamic exchange" model of ion association proposed by Watanabe and Hamaguchi, [J. Chem. Phys.123, 034508 (2005)] for aqueous solutions of MgSO4 is shown to be inconsistent with the extensive information available from Raman, relaxation, and thermodynamic studies, all of which can be explained by the Eigen equilibrium model.