Modelling of acid–base equilibria in binary-solvent systems: A comparative study

A new approach to modelling of some binary (hydro-organic, HL/H2O + B) acid–base systems with organic co-solvent B fully miscible with water, is suggested and applied for the determination of acidity parameters pK for some weak acids HL. The models are designed to get the pK = pK(x) relationships (x—mole fraction of B in H2O + B) from results of pH titrations made in such systems and for the determination of pKB = pK(1) for HL in pure B. The Redlich–Kister equation, together with its asymmetric extensions, and the Legendre functions with orthogonal polynomials, appeared to be suitable for such purposes.