Studies on the electrical double layer structure at the water/air interface

Abstract

Effective dipole moments (calculated from experimental data of surface tension and electric surface potential) of some homologous normal alcohols and carboxylic acid were found to vary linearly with the number of carbon atoms in the hydrocarbon chain. Values of effective dipole moments were used for the determination of the effective dipole moments of water molecules\((\bar \mu _{{\text{H}}_{\text{2}} {\text{O}}} )\), and the dielectric permittivity of the water subphase (e1), as well as in the vicinity of the hydrophobic part of adsorbed molecule (e2). The latter was found to decrease with the increase of the hydrocarbon chain length. Knowing the effective dipole moment of surface water dipoles, the average orientation angle (α) of water molecules at the inteface was estimated. The calculated potential drop of water varies within the range −0.038 to −2.38 V for two extreme orientations of water dipoles at the surface.