The idea of partial dissociation of electrolytes proposed by Arrhenius in 1883 was a great success in explaining many properties of solutions of electrolytes. While the theory was still being developed to account for the non-ideal properties of electrolytes at higher concentrations, it was immaturely replaced by the empirical concepts of activity and activity coefficients by Lewis (1921) despite protests by many. With the near success of the Debye-Huckel (1923) theory of inter-ionic interactions for complete dissociation in very dilutions, this theory was erroneously extended over the next few decades by longer and longer parametrical equations to fit the data for higher concentrations assuming complete dissociation. This eventually turned solution theory into a mere catalogue of parameters. Therefore, the present author started systematically analyzing the available experimental data as such. The gradual stepwise successes (since 1977) led ultimately to the finding in 1994 that with the degrees of dissociation and ‘surface’ and ‘bulk’ hydration numbers evaluated from vapour pressure data, the non-ideal properties of electrolytes could be explained quantitatively from zero to saturation. Simple mathematical equations involving actual ionic concentrations (not ionic activities), hydration numbers and volumes of the dissolved species were established to explain the experimental data. Thereby, the earlier theory due to Arrhenius was successfully restored. Another important result, namely the absolute potential of the standard hydrogen electrode (which, due to the lack of its knowledge, was arbitrarily set as zero) was obtained by the author (2009) by correlating the gas phase ionization potentials with the aqueous standard potential data. This enabled the establishment of the absolute potentials of standard electrodes and of many redox couples of the elements of the Periodic Table. All the data have been published in open access articles.
Buy this Article