THERMODYNAMICS OF IONS OF CHROMIC AND THIOCYANIC ACIDS - SOLVATION INTHE ETHANOL-WATER SYSTEM

The standard electrode potential of Ag/Ag2CrO4 and Ag/AgSCN electrodes in the ethanol-water system (with 0, 10, 30, 50, 70 and 0, 10 30, 50, 70, 90, 200 wt.% of ethanol, respectively) has been determined vs. an Ag/AgCl electrode in a liquid-junction cell in the temperature range 278.15-338.15 K. Solvation thermodynamic functions of stoichiometric m ixtures of(2H(+), CrO42-) and (H+, SCN-) ions have been calculated on the basis of the temperature dependence of the emf. The Gibbs energy o f solvation has been divided into ionic contributions using the refere nce electrolyte extrathermodynamic assumption. The addition of alcohol to water has been observed by Gibbs energy of transfer analysis to re duce the stability of the complexes formed between chromic acid ions a nd solvent molecules, but to improve this stability in the case of thi ocyanic acid.