Ionization and Hydration Equilibria of Periodic Acid

Abstract

Variations in the absorption characteristics of periodate solutions with pH and temperature have been used to better determine the species present in dilute aqueous solutions. The species H5IO6, H4IO6−, IO4− and H3IO6− and their equilibria were sufficient to completely explain the spectrophotometric and potentiometric data of periodate solutions in pH ranges 0-7 and temperature ranges 0-70°. Apparent and true constants for these ionization and hydration equilibria have been evaluated at 25° as αH+(αH4IO6−)/αH5IO6 = K1 = 5.1 × 10−4 αH+(αH3IO6−)/αH4IO6− = K2 = 2.0 × 10−7 (αIO4−/(αH4IO6−) α2H2O = KD = 40 [αH+(αIO4− + αH4IO6−)]/αH5IO6 = K1´ = 2.3 × 10−2 αH+(αH3IO6−)/(αIO4−+ (αH4IO6−) = K2´ = 4.35 × 10−9. © 1951, American Chemical Society. All rights reserved.