Specific adsorption at the mercury/methanol interphase

Abstract

The orientation of methanol molecules in the mercury/methanol interphase has been investigated by studying the temperature coefficient of the potential of the point of zero charge and the adsorption of di-n-butyl ether. The results suggest that when the mercury is uncharged the methanol dipole is oriented with the negative end towards the mercury. The adsorption of iodide ions and of thiourea at this interphase has been studied by measuring capacity and electrocapillary curves. Both adsorbed species obey isotherms with a standard free energy of adsorption which is a linear function of the charge on the metal. The parameters representing the interaction between the adsorbed particles are charge dependent; this dependence is greater for iodide ion than for thiourea. The two-dimensional second virial coefficient for thiourea is comparable with the values found for this substance in aqueous and formamide solutions. In contrast, the second virial coefficient for iodide ion is considerable larger than in the other two solvents.