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Summary. The pathways for the oxidation of tartaric acid and citric acid by vanadium(V) in perchloric acid medium have been studied at 303?K by following the formation of vanadium(IV) spectrophotometrically at 760?nm. The oxidation reaction displays fractional order dependence with respect to both the a-hydroxy acids concentrations as well as fractional (tartaric acid) and first order (citric acid) dependencies with respect to the perchloric acid concentration. It does not matter at all whether the ionic strength was varied or was maintained constant. The reaction rate remains essentially constant with increasing ionic strength in the tartaric acid oxidation, but decreases slightly in the citric acid case. A decrease of the dielectric constant of the reaction medium results in a rate decrease in the tartaric acid oxidation and in a rate enhancement in the citric acid reaction. The activation parameters were obtained from studies of the reactions at different temperatures (293 to 313?K). Based on the experimentally determined rate laws oxidation mechanisms and theoretical rate laws were proposed. [ABSTRACT FROM AUTHOR]