ELECTROLYTIC CRYSTALLIZATION OF SILVER AT PLATINUM AND IRIDIUM IN NITRATE SOLUTIONS - THE INFLUENCE OF A PRELIMINARY CATHODE TREATMENT

The influence of a preliminary anodic treatment and cathode material ( platinum, iridium) on silver nucleation is studied in an individual Ag NO3 melt and dilute AgNO3-NaNO3-KNO3 solutions. An increase in the pot ential and duration of the anodic treatment, which leads to a more pas sive state of the cathode surface at the expense of a strong oxide fil m forming at the cathode, results in a greater nucleation overvoltage reached in a longer time and in a decreased number of silver nuclei. T he way of anodic treatment strongly affects the charge consumed prior to reaching a maximum nucleation overvoltage and the electrode capacit ance. The iridium substrate is found to be more inert than the platinu m one. The nucleation work rises with the anodic treatment potential. In dilute solutions, the influence of differences in the anodic treatm ent is manifested more weakly.