REDUCTION AND AGGREGATION OF SILVER IONS IN AQUEOUS GELATIN SOLUTIONS

Radiolytic reduction of silver ions and the subsequent formation of si lver clusters were studied in aqueous gelatin solutions and are compar ed with the parallel processes in aqueous solutions. The presence of g elatin in the solution affects the early processes, via complexation o f Ag+ ions with the amino acid moieties of the gelatin. The ratio of A g+ to gelatin chains predetermines the kinetic consequences to the agg lomeration processes. This ratio may accelerate or inhibit any of the processes that involve silver ions (reduction as well as growth). The complexation reduces somewhat the rate of reduction by hydrated electr ons. However, when all the ions are complexed to the gelatin, the aggl omeration may become very fast; at the extreme the agglomeration rate is determined by the rate of reduction. Some of the small Ag-n(m+) bin d to the gelatin stronger than Ag+ ions. Excess silver ions enhance th e stability of smaller transient clusters in the presence of gelatin. Three long-lived aggregates of different sizes are stabilized by the g elatin upon complete reduction of the silver ions.