Two-dimensional condensation in camphor-10-sulphonic acid films at the mercury/electrolyte interface.

The electrocapillarity and the barrier properties of camphor-10-sulphonic acid (CS) in various aqueous electrolytes (1 M NaSO, 3 M LiClO, 2 M KNO, 3 M KCl, 3 M KBr) were studied. From the electrocapillary curves the charge-density-potential and the surface-pressure-potential-curves were calculated and analyzed using the Lippmann-Helmholtz and Gibbs-equations. The cross-sectional areas a of CS, resulting from the maximum excess surface concentration, suggest a perpendicular orientation of CS-molecules in the condensed film at the potential of maximum adsorption. This orientation causes a dense packing and a strong interaction between the CS-molecules in the condensed film. The barrier properties that represent the reduction of Cu-ions in the presence of the adsorption layer were studied dc polarographically at high surface coverage. A change in the inhibition mechanism was observed due to the change of the structure in the adsorptions layer. The electrode reaction is strongly inhibited within the potential and concentration range of film condensation. [ABSTRACT FROM AUTHOR]