The Chemical Iodination of Silver

Abstract

Kinetic experiments are reported on the chemical formation of AgI layers on polycrystalline silver substrates. The AgI layers, up to several micrometres in average thickness, were grown under ambient conditions by reacting a rotating silver disc with solutions of iodine dissolved in ethanol and with aqueous triiodide solutions. The morphology and structural identity of the AgI layers were determined by scanning electron microscopy and powder X-ray diffraction, respectively. Depending upon the growth conditions employed, either porous or compact AgI deposits could result, and thus the rate of formation of AgI could be limited by a diffusion step in solution, or by some slower transport step across the layers. The AgI layers were inhomogeneous, and often consisted of discrete crystallites. Thus, the metal oxidation theories developed for planar and isotropic product layers could not be applied to the formation of AgI layers under ambient conditions.