Chapter 5: Experimental Determination

In Chapter 5, the approaches employed for the experimental determination of thermodynamic parameters related to ionic solvation are reviewed, and the results of investigations employing these methods are discussed in the restricted context of alkali and halide hydration in the infinitely-dilute regime. Closely related properties formally pertaining to the pure solvent (water), namely the absolute solvation parameters of the proton, the absolute potential of the reference hydrogen electrode and the air-liquid interfacial potential, are also considered in view of their central role in single-ion solvation thermodynamics, in both their real and intrinsic forms. The discussion proceeds roughly incrementally, from the most directly accessible quantities to the more elusive ones, namely: (i) molar thermodynamic parameters of the elements; (ii) structural and molar thermodynamic parameters of the salts (ionic crystals); (iii) gas-phase equilibrium ion-pair distances; (iv) effective ionic radii; (v) relative electrode (redox) potentials (anchored based on the reference hydrogen electrode); (vi) thermodynamic parameters of salt formation; (vii) thermodynamic parameters of dissolved salt formation; (viii) thermodynamic parameters of salt dissolution; (ix) thermodynamic parameters of atomization; (x) thermodynamic parameters of ionization; (xi) thermodynamic parameters of reticulation; (xii) thermodynamic parameters of salt solvation; (xiii) metal workfunctions; (xiv) real absolute potential of the reference hydrogen electrode; (xv) real single-ion solvation parameters; (xvi) conventional single-ion solvation parameters; (xvii) air-liquid interfacial potential of the pure solvent; (xviii) intrinsic proton solvation parameters. Three additional sections provide: (i) a summary of recommended data concerning alkali and halide hydration, along with relevant pure-solvent properties; (ii) a discussion of suggested intrinsic single-ion solvation parameters for the alkali and halide ions, in connection with the Hofmeister series; (iii) a brief discussion of the properties of the solvated electron. The recommended data is based on the careful investigation of experimental results from 221 literature sources over the past nearly hundred years. This data is presented in the form of a minimal (non-redundant) set of parameters concerning the gas-phase, salt and solution properties the alkali and halide ions, as well as of the proton, with reference to water as a solvent, converted to a unique standard-state convention (bbme_T convention).