Seawater samples were collected using a technique that isolated the upper 0.15 mm of surface water.Much of their organic matter was surface-active, slick-forming material that was originally at the seawater-air interface. These surface-active molcculcs are of interest because of their influence on many properties of the sea surface. Determinations were made of the effect of monolayers of these materials on the surface tension, on the surface potential, on the damping of capillary waves, ancl on the surface viscosity.The measurements were made as functions of the area of surface occupied by the adsorbed molecules.

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Each of the homologous series of pure n-fatty acids from C1 to C26 has been studied as a condensed monomolecular layer adsorbed on Pt a,nd NiO substrates. Both the CI8 and CIS acids were also studied on various polished metal surfaces including Fe, Cr, Cu, Au, W, Mo, Ag, Nb, Al, Cd, Mg, Sn, Pb, Be, Zn, and Ni. The change in conta.ct potential difference (AV) between the metal and an aged reference electrode was measured in air a t 23' and 50% R.H. Surface packing in each nionolayer was characterized by the methylene iodide contact angle (e). Systematic and reproducible values of AV and 8 were found for each member of the homologous series. An asymptotic maximum occurred in the AV us. N curves when N , the number of carbon atoms per adsorbed molecule, was 14 or more for Pt and NiO substrates. Alternation of AV occurred for odd and even values of N on NiO and the baser metals but not on Pt and Au. Values of 8 for stearic acid varied with the nature of the metal substrate, and the results were in reasonable accord with the lattice spacing of the substrate atoms. Values of A V for stearic acid monolayers varied from a maximum of 0.365 v. on W to -0.095 v. on Pb, and it was concluded that the perpendicular component of the dipole moment of the adsorbed acid niolecule was a function of the specific interaction of metal substrate and the acid carboxylic group. Stearic acid desorbed readily from Pt but not from NiO, and it was concluded that chemisorption had occurred on the NiO. The contributions from adsorbed water, oxides, and induced polarization in determining AV are discussed.

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