not listed in Table I, were tested by compressing the film spread a t low pressures. Cyclohexyl myristate and also ethyl oleate gave easily compressible films producing very little reduction in the rate of evaporation. Methyl stearate on compression from 0.3 to 11 dynes/cm. reduced the rate of evaporation by a practically constant value of 12%. Lauryl alcohol gave a low resistance to evaporation which was practically constant (0.21 to 0.37) over a wide range of pressures (1.4 t o 41 dynes/cm.) .With arachidic acid even at nondiscernible pressures, there is a noticeable eflect (reduction of 15%) on the rate of evaporation. On compressing this film the rate decreased rapidly as soon as discernible pressures were noted until a t about 22 dynes/cm. the rate of evaporation becomes 60% of that of pure water.Acknowledgment.-H.

Using 2 MeV lithium ions backscattering and transmission electron microscopy techniques, some of the xenon atoms introduced by implantation in aluminum metal under the initial oxide layer are shown to be transported by the moving metal-oxide interface during anodic oxidation. For specific anodization conditions (V at, T : 90~ this splitting of the initial xenon distribution is interpreted in terms of bubble formation and growth above a given local concentration threshold. A schematic model for this behavior evolution is proposed. This dose dependance is of practical interest in the determination of transport numbers. Although unambiguously measured they may be subject to significant systematic uncertainties which are discussed.

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