SURFACE POTENTIALS AND INDUCED POLARIZATION IN NONPOLAR LIQUIDS ADSORBED ON METALS.
NAVAL RESEARCH LAB WASHINGTON DC
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The contact potential difference between a metal and a suitably coated metal serving as a reference electrode can be used in clean air as a sensitive and reliable tool for studying adsorbed monomolecular films of polar compounds. The change Delta V in the contact potential difference resulting from the adsorption on a metal of a film is reported for each of the following pure, nonpolar liquid compounds hexane, octane, decane, dodecane, tetradecane, hexadecane, cyclohexane, dicyclohexyl, benzene, toluene, xylene, and carbon tetrachloride. Clean polished surfaces of Pt, Au, Ag, Cu, Ni, W, Cr, Sn, and Cd were the adsorbing metals. Contact angles of water, glycerol, methylene iodide, and hexadecane on the same adsorbed films supplied information about their nature, packing, and orientation. The following conclusions can be made a evaporation of the liquid always leaves on the metal an adsorbed monolayer oriented so that the maximum number of atoms contact the surface b when excess liquid is wiped off the metal by rubbing with clean filter papers, a monomolecular adsorbed film remains whose properties are identical with those obtained by evaporation c the electrostatic image field of the adsorbed molecule is not sufficient to cause the observed values of Delta V and the parameters involved include the lattice spacing and atomic volume of the metal. Author