Surface and electric properties of n-octyl-beta-D-gluco-pyranoside (OGP) at the air/water interface

Surface pressure (pi - using De Nouy ring), and electric surface potential (Delta V - using vibrating plate method), were measured on free surface of "surface-chemically pure" solution of n-octyl-beta-D-gluco-pyranoside (OGP) in pure water. The obtained surface excess (Gamma) and surface potential ( Delta V) vs. concentration (c) isotherms fall consistently in the concentra tion range of about 1 * 10(-5) to 2 * 10(-2) mol/dm(3) OGP. The pi vs. c da ta can be well described in terms of the Frumkin adsorption isotherm. The d ependence of the Delta V on the surface excess (Gamma-Frumkin) is fairly li near in the entire adsorption range, implying a constant effective dipole m oment of OGP molecule - the mu(perpendicular to i)/epsilon(s) amounting to 0.32 +/- 0.04 D per molecule.