Equilibria in aqueous solutions of iodic acid

Abstract

Precise measurements have been made on aqueous iodic acid solutions with concentrations up to 0.1 M by conductimetric, potentiometric and kinetic methods. New conductimetric results are also reported for potassium iodate solutions. Stoichiometric activity coefficients of iodic acid were obtained by combining the e.m.f. of concentration cells with transport numbers. Hydrogen ion concentrations were obtained from the rates of catalytic inversion of sucrose solutions. The three independent sets of results can all be fitted with the values 5 Å for the ion-size parameter, 0.157 mole l.^–1 for the acidity constant and 4 1. mole^–1 for the stability constant of the ion H(IO₃)^–₂. It is shown that misleading conclusions are easily reached by reliance on a single technique. The existence of the complex ion is confirmed by re-analysis of cryoscopic data. The results of other measurements on iodic acid solutions are discussed.