KINETICS OF ALUMINUM ION HYDROLYSIS IN DILUTE SOLUTIONS

Dissociation field effect relaxation times in dilute aqueous aluminum chloride have been measured and attributed to the perturbation of the hydrolysis equilibrium Al3+ + H2O ⇌k1k-1 AlOH2+ + H+ rather than complexing or dimerization equilibria. At 25° the specific rate k-1 = (4.4 ± 0.5) × 109 M-1 sec-1 at an ionic strength μ ≅ 1 × 10-3 M. This result is consistent with measured rate constants for other essentially diffusion-controlled protolytic reactions H+ + M(n+)-1 → for which n varies from 0 to 3.