where r is the rate in moles sec -1 cm -2, c is the concentration of KNO3 in moles liter -1, and Po and E are constants.The activation energy, E, is 17.1 kcal mole -1 and Po, which can be regarded as a frequency factor, was found to be 9.2 x 106 cm sec -1. DiscussionCapacitance studies (1) have revealed that freshly prepared anodic zirconium oxide films are permeable to electrolyte solutions, but microscopic evidence indicates that the surface of the oxide is virtually featureless (3). Several suggestions have been made to account for this permeability, the most reasonable being the existence of invisible cracks perpendicular to the film surface (4). Our experimental observations lead to some tentative conclusions about the nature of the oxide film and the permeation process.The permeation rate is fairly reproducible. The small deviations in results can be attributed to variations in the ratio of actual film area to apparent film area. This indicates that a reproducible network of interstices, rather than random gross flaws, serve as paths for permeation. Furthermore, the activation energy for the free diffusion of KC1 in water is 4.4 kcal mole -1 (5) which is nearly four times smaller than the observed activation energy for permeation through the oxide. This also supports the contention that the process is not merely a simple bulk diffusion through large flaws.The relative concentration independence of the constant, P, is difficult to account for if a pore-free barrier layer similar to that found in porous anodic aluminum oxide (6) exists at the oxide-dilute solution interface.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.210.126.199