Electrostatic .and .hydrophobic interactions of ions near interfaces
are examined in relation to the nature and structure of surfaces
of. liquids, esp~cia.lly that of water.
The superficial excess entropy and energy of liquid surfaces is
calculated from surface tension data, aind Stefan\u27s ratio is evaluated
for several liquid interfaces. Stefan\u27s ratio is related to the ratio
of co-ord~nation number of surface molecules to that for bulk
molecules and leads to information on surface structure. Stefan\u27•s
ratio is ca. 0.5 for non-polar liquids but is near 0.1 for H-\u27bonded
liquids. The superficial excess entropy is related to the cohesive
energy density and to co-ordination i,n the surface.
Short-range ·effects in adsorption of ions at air/water interfaces
are determined by the structure of the liquid surface and by
electrostatic polarization energy near the interface. Based on the
Born equation, relations are · deduced for ionic adsorption near
liquid interfaces. By studying the adsorption of a series of propylamine perchloratesat the air/water interface and the correspond1ng surface
potential changes, the relaEve . importance of hydrophobic and
electrosrtatic ion-solvent interaction effects was investigated.
Methods for investig~ting the entropy of water at charged
interfaces are discussed and a theory of entropy of water· in the
double-layer is reviewed
