The ionic desorption transition found recently in a statistical field approach to electrified interfaces is discussed in relation to the experimental data on the interfacial capacitance of mercury in contact with various electrolyte solutions. The model reproduces qualitatively, a common feature of the experimental data in various solvents, which is the branching of the capacitance curves for electrolytes having various degrees of specific adsorption on mercury from the virtually common curve, which is independent of the nature of the electrolyte.