A method is presented to determine, individually and with minimal extra-thermodynamic assumptions, the Gibbs energy for anion transfer between two solvents using solid state electrochemistry of alkynyldiphosphine dinuclear Au(I) complexes (AuC(2)R)(2)PPh(2)C(6)H(4)PPh(2) (L1, R = Fc; L2, R = C(6)H(4)Fc) and the heterometallic Au(I)-Cu(I) [{Au(3)Cu(2)(C(2)R)(6)}Au(3)-(PPh(2)C(6)H(4)PPh(2))(3)](PF(6))(2) (L3, R = Fc; L4, R = C(6)H(4)Fc) cluster complexes containing ferrocenyl units. These compounds exhibit a well-defined, essentially reversible solid-state oxidation in contact with different electrolytes, based on ferrocenyl-centered oxidation processes involving anion insertion. Voltammetric data can be used for a direct measurement of the free energy of ion transfer from one solvent. to another using midpeak potentials in solutions of suitable salts in each one of the solvents separately or mixtures of the solvents. Excess Gibbs energy of solvation in solvent mixtures can also be directly measured using this procedure. Solvation data for different common inorganic oxoanions in water, MeOH, and MeCN and water-MeOH and water-MeCN mixtures are provided.