Analytical study of the reduction of chromium(VI) by d-galacturonic acid

The reduction of chromium (VI) to chromium(III) by d-galacturonic acid takes place to a significant extent only in the presence of metal ions such as copper(II) or chromium(III) itself. These metals can form stable complexes in which the opening of the sugar ring leads to a reducing free aldehydic group. The stoichiometry of the reaction, the dependence of the yield on the nature of the metal ion and the pH of the solution and the products formed, were studied. Stoichiometries and stability constants of the complexes present in the system chromium(III)-d-galacturonic acid were evaluated.