The adsorption of aromatic sulphonates at a mercury electrode. Part 1.—Sodium benzene m-disulphonate

Abstract

The adsorption of the benzene m-disulphonate ion on a mercury surface from aqueous solution has been studied by measuring the interfacial tension and the capacity of the electrode as a function of concentration at four temperatures. The adsorption can be fitted by a Temkin isotherm from which the amounts adsorbed are obtained. The inner layer capacity is analyzed into its components and these are related to the thicknesses of the inner and outer Helmholtz layers. The breakdown of the assumption that adsorbed anions produce a constant field in the inner layer is discussed and a reliable method for calculating the potential at an anion site and Stern's specific adsorption potential is proposed.

Specific adsorption of sulfamate ions at the mercury/solution interface

“…In the region 3 < q < 7 pC ~m -~, average values of ,K1 and ,,K1 can be used (9) to give an indication of the relationship between the distances from the metal to the inner Helmholtz plane (i.H.p., x,) and from the metal to the 0.H.p. (x,).…”

“…2 and 7). This isotherm can be derived from detailed electrostatic models of ionic adsorption (8) or from more simple approaches (7,9,10). It has even been used as a working hypothesis to discuss the entrance of counter-ions in the inner layer (11).…”

On the electrical double layer between mercury and aqueous solutions of sodium citrate

“…It is evident that g is smaller than the unit, as in the case of the azide ion (15) and the benzenedisulfonate ion (12). Given the experimental errors, g is practically independent of charge (see Table 3) supporting the prediction that the potential drop across the inner layer is additively composed of contributions from the layer on the metal and from the charge on the adsorbed layer.…”

Temperature dependence of the potential of zero charge at the mercury/potassium iodide aqueous solution interface

“…Anderson and Parsons [1] performed electrocapillary surface measurements of the KI aqueous solutions at 5, 25 and 45°C. Similar studies have been carried out with sulphonate anions by Parry and Parsons [2]. Grahame [3] measured the thermal coefficients of E z in NaF solutions in the 0-85°C temperature range by the capacity method.…”