Capillary Electrophoresis and its Basic Principles in Historical Retrospect. Part 4. Svante Arrhenius´ Electrolyte Dissociation. From 56 Theses (1884) to Theory (1887)

Since the main interest of Svante Arrhenius, a student at Uppsala University, was electrical conductivity highly dilute electrolyte solutions, which had not yet been determined beginning 1880s, he decided to determine experimentally molecular conductivities aqueous solutions about fifty electrolytes and their dependence on dilution. In his dissertation, began in winter 1882/1883, summarized results considerations 56 "theses". He observed that strong acids high conductivity, increased only slightly with increasing Weak acids, contrast, low conductivities, but these abruptly above certain Arrhenius' innovative hypothesis molecules are composed from two parts, "an active (electrolytic) an inactive (non-electrolytic) part," proportion part dilution expense part. Moreover, electrically part, conducts electricity, also chemically Arrhenius introduced activity coefficient, later quoted as degree dissociation, indicated sum molecules. tentatively related coefficient conductivity. assumed higher coefficients different same equivalent concentrations, stronger they are. tested taking heat neutralization base measured by Thomsen Berthelot. Strong developed highest heats, i.e., activation water, since consisted entirely H+ OH- ions, combined H2O. correspondingly less. The established parallelism between heats first proof hypothesis. relied thermochemistry completed dissertation. presented dissertation June 1883 published it 1884 obtain doctorate. At time, Wilhelm Ostwald investigating affinities bases, i.e. intensity effects rates reactions cause. took rate constants measure relative strength acids. After receiving thesis, acid´s found remarkable proportionality reaction hydrolysis methyl acetate inversion cane sugar caused them. This second hypothesis, based chemical kinetics. A memoir 1885 J. H. van 't Hoff analogy osmotic pressure solution separated pure solvent semipermeable membrane ideal gas containing number particles led probably most convincing corresponded Avogadro's well-known law, is PV=RT. for non-conductors such glucose followed this electrolytes. deviation accounted factor i, indicates into how many solute - least partially has dissociated, so modified law PV=iRT. i could be deduced Raoult's freezing point depression, calculated using dissociation α. turn, ratio under limiting conditions. agreement factors independent methods third There fourth proof, namely additivity physical properties. With four nonelectrical proofs, theses became groundbreaking theory substances dissolved 1887. 1903 Nobel Prize Chemistry awarded him "in recognition extraordinary services rendered advancement chemistry electrolytic dissociation”.