Electrical double layer at the interface between mercury and dilute aqueous electrolyte solutions

Abstract

Differential-capacitance/potential curves were measured at the interface between mercury and dilute aqueous solutions of HClO 4, NaClO 4, NaOH, CH 3COOH and NH 4OH. In the potential region near the zero-charge potential, the double-layer behaviour of these systems is in agreement with Grahame's theory. In the negatively polarized region, the double-layer capacitances of the strong electrolyte systems decrease with decreasing concentration; this result suggests that the complete formation of the compact double-layer becomes difficult in very dilute solutions. The double-layer properties of CH 3COOH and NH 4OH solutions were compared with those of the strong electrolyte solutions. The difference between the weak and strong electrolyte systems in the differential capacitances in the negatively polarized region is explained in terms of the dissociation field effect on weak electrolytes.