Water Structure around Silver Iodide Sol Particles

Abstract

IN order to explain lower values of differential capacity at the negative silver iodide/solution interface than at the mercury/solution interface, Lyklema¹ proposed that the Stern layer in the former may be of icelike (tetrahedral) structure, and pointed out that this would also explain the greater specificity of cations in the silver iodide case. More recently Levine and Bell² have commented that such structure would tend to remove the distinction between inner and outer Helmholtz planes so that the fluctuation potential would become small, this making the maximum in the outer Helmholtz plane potential much less marked. This effect would then explain the relative constancy of the flocculation concentration for silver iodide sols at high (negative) potentials^3,4 compared with those of silver bromide and silver chloride sols, which have been reported⁵ to decrease at high negative potentials. The hypothesis is supported by the well-known epitaxis of ice on silver iodide which is more effective near the zero point of charge⁶.