Rate constants and concentration equilibrium constants for the chemical reaction between the mono and dioxalato complexes of Ti(IV) were determined from experiments in square wave voltammetry in the H+ range 0.5-1 M and in 0.03 M H+. It was concluded that in strong acid media the reaction must be: Ti(OH)(2)C2O4 + C2O42- reversible arrow Ti(OH),(C2O4)(2)(2-). In 0.03 M H+, the nature of the mono oxalato complex changes and H+ is involved in the reaction of formation of Ti(OH)(2)(C2O4)(2)(2-). (c) 2005 Elsevier B.V. All rights reserved.