Electric field effects on monolayers at the air-water interface

Application of an electric field to insoluble monolayers at an air-water interface is shown to induce changes in surface pressure and monolayer density which correlate with surface potentials in accordance with a recently published thermodynamic analysis using Gibbsian methods. For twocomponent monolayers, the interdependence of local fields and composition has been demonstrated qualitatively. The results provide experimental proof that the thermodynamic treatments of the Volta effect due to Kelvin, Lorentz and Bridgman are incorrect. These treatments essentially ignore the dependence of the interfacial structure of oriented dipoles on the applied field. Correspondingly, the experimental results open up novel approaches for relating these interfacial structures to interfacial potentials.