KINETICS OF REDUCTION OF SILVER(I) GELATIN COMPLEX IN AQUEOUS ALKALINE-SOLUTION

The kinetics of reduction of silver (I)-gelatin complex by ascorbic acid and hydrazine has been studied spectrophotometrically with trace concentration of reducing agents in alkaline medium with low ionic strength (<0.1 M) in the temperature range 15-degrees-41-degrees-C. The reduction is first order each in both the reactants with an inverse first order dependence on [H+] for ascorbic acid oxidation and shows an almost zero order dependence on [H+] for hydrazine oxidation. The activation parameters are found to be DELTAH(not-equal) = 20.67 +/- 2.5 kJ mol-1, and DELTAS(not-equal) = -24.1 +/- 4.5 J K-1 mol-1 for the reduction of the complex by ascorbic acid while those for the reduction of silver (I)-gelatin complex by hydrazine were found to be 23.72 +/- 2.05 kJ mol-1 and 12.3 +/- 2.5 JK-1 mol-1, respectively. A tentative mechanism consistent with the kinetics is discussed.