Experimental evidence is presented that the catalytic reduction of Ti(W) in oxalate-chlorate media is affected by the rate of the chemical reaction between the mono (S-1) and the dioxalato (S-2) electroactive complexes of Ti(IV). A theoretical treatment enabled us to specify that the step responsible for the catalytic effect in the reaction process is the homogeneous oxidation of Ti(Ill) to S-2. The experimental results were quantitatively interpreted and the conditions for the analysis of Ti(IV) were defined. (c) 2005 Elsevier B.V. All rights reserved.