Thermodynamic Functions of Transfer of Single Ions from Water to Nonaqueous and Mixed Solvents Part 4: Selection of Extrathermodynamic Assumptions

The selection of an extrathermodynamic assumption for the division of standard thermodynamic functions of transfer of electrolytes from a reference solvent to other solvents is discussed. Reasons for choosing water as the reference solvent are given. Advantages and drawbacks of approaches concerning the Gibbs energy of transfer: real potentials, negligible liquid junction potential, electrostatic models, extrapolation methods, reference ion, reference ion/molecule redox couple, and reference electrolyte, are discussed. The least objectionable is the last one, with tetraphenylarsonium (or -phosphonium) tetraphenylborate as the reference electrolyte. This has the additional advantage that it can be applied also to enthalpy and entropy of transfer data.