Discreteness‐of‐charge‐effects in the inner region of the electrical double layer

The effects of the discreteness of adsorbed ionic charge in the electrical double layer have been examined. The formula of Esin and Shikov [2] for the ratio of the micropotential to the macropotential has been confirmed. In agreement with Ershler [3] it is concluded that if one neglects the multiple reflection of adsorbed ions between the outer Helmholtz plane and the metallic surface, a contradiction with experiment appears. Taking these into account it is shown that the potential developed by a layer of adsorbed ions between two reflecting planes, or between air and one reflecting plane, is just half what one would compute if no reflecting planes were present and if in place of the first reflection of the adsorbed ions real charges were present at the image positions in the solution. The formula of Ershler for the rate of change of the potential of the electro‐capillary maximum with respect to the activity of an adsorbed electrolyte has been reexamined and extended to include charged as well as uncharged surfaces. An adsorption isotherm for anions on a metallic or airsolution interface has been derived and methods found for the evaluation of the potential of the inner Helmholtz plane.