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Vol. 59 these surfaces. The significant decreases observed for the autophobic contact angles with dehydration of the crystals mean that the acids and alcohols adsorb less well-oriented on the dehydrated surface. This can be explained readily if the principal mechanism in the oriented adsorption of these polar compounds on silica and «-alumina is through hydrogen bonding with the adsorbed water. When this cannot occur the molecules will adsorb lying more nearly in the surface.Acknowledgments.-It is a pleasure to thank Mrs. Elaine Shafrin for helpful discussions. We are indebted to Prof. R. Schiessler and The American Petroleum Institute for the several synthetic hydrocarbons (designated as .PSC compounds) which were prepared by A. P. I. Project 42.