Dissolution behavior of silver in ammoniacal solutions using bromine, iodine and hydrogen-peroxide as oxidants

The dissolution behavior of silver in ammoniacal solutions in the presence of bromine, iodine and hydrogen peroxide as oxidants has been studied. The effect of concentrations of ammonia and oxidants, and pH of the solution on the rate of dissolution of silver powder was investigated.Silver dissolution was greatly affected by the ammonia concentration as well as concentrations of oxidants. The higher the concentration of oxidants, the greater the silver dissolution. However, high concentrations of halogen based oxidants resulted in precipitation of silver unless sufficient ammonia was also present. It was also noted that the silver dissolution is a strong function of pH of the solution. The optimum values of pH were found to be in the range 9–10. This behavior was explained in terms of the thermodynamic stability data of silver (I) complexes with halogen-based oxidants as a function of pH.