Pairwise interaction parameters for sodium, potassium and halide ions in aqueous solutions

Abstract

Practical osmotic coefficients for mixed aqueous solutions at 298.15 K and ambient pressure containing alkylammonium and alkali-metal salts are examined from the standpoint of a composite salt having the stoichiometry (1 –y) M⁺yR₄N⁺X^–, where X^– represents an anion. Practical osmotic coefficients for these aqueous solutions are estimated assuming that ion–ion interactions are satisfactorily accounted for in terms of charge–charge interactions. Differences between observed and calculated practical osmotic coefficients are assigned to interactions between cospheres surrounding ions in solutions. For alkylammonium and substituted alkylammonium ions these interactions are expressed in terms of group interaction parameters. Cosphere interaction parameters are reported for Na⁺, K⁺, Br^– and Cl^– ions, together with interaction parameters for OH groups in substituted alkyammonium ions. Derived group interaction parameters are used to comment on trends in Setschenow coefficients for amides and volatile hydrocarbons in aqueous salt solutions.