ON THE THERMODYNAMIC STABILITY OF CONDENSED URACIL FILMS FORMED AT THE MERCURY ELECTROLYTE INTERFACE IN THE PRESENCE OF DIFFERENT SUPPORTING ELECTROLYTES

The thermodynamic properties of condensed uracil films formed at the mercury/electrolyte interface were studied in the presence of different supporting electrolytes (constant ionic strength) by measuring the interfacial impedance at 10 kHz. The experimental results were analysed by applying the classical Frumkin model and the lattice-gas model. The latter yielded more reliable data for the condensed region. On the basis of the pit width, the condensation and critical temperatures, the Gibbs energies of adsorption and the pair interaction energies, the following stability sequence follows: F- almost-equal-to SO42-almost-equal-to ClO4- < NO3- < Cl- < Br- < SCN- < I-. The intrepretation of the data is based on changes in the bulk phase and the interfacial region due to the presence of structure-breaking and structure-making anions. The role of stacking interactions and the hydrogen-bond formation for the stability of condensed uracil films indicate that the pair-interaction energies characterize primarily hydrophobic interaction forces.