The hydrolysis of metal ions. Part 8. Aluminium(III)

Abstract

An automated potentiometric titration technique has been used to study the hydrolytic behaviour of the aluminium(III) ion in 0.10 mol dm–3 sodium nitrate at 25 °C. Low aluminium(III) concentrations (up to 0.1 mol dm–3) were used so that the monomeric species, [Al(OH)]2+ and [Al(OH)2]+, could be identified. The data treatment indicates the presence of the species [Al(OH)]2+, [Al(OH)2]+, [Al3(OH)4]5+, and a high-molecular-weight polymer with a q/p ratio (OH/Al) of ca. 2.46 and a p value between 6 and 14. The –log βpq values for these species {βpq=[Alp(OH)q(3p–q)+][H+]q/[Al3+]p} are estimated to be 5.33 (0.009), 10.91 (0.04), 13.13 (0.005), and 5.73 – 3.6p+ 4.64q(0.04) respectively, the estimated standard deviations being given in parentheses.