The properties of the electrical double layer at a dropping mercury electrode in n‐potassium chloride containing n‐alkyltrimethylammonium ions

Abstract

In further experiments on the adsorption of n‐alkyltrimethylammonium corrosion inhibitors at a dropping mercury electrode in N‐potassium chloride solution, the potential applied to the dropping mercury electrode was taken as far as ‐1.9 volts S.C.E. The electrocapillary and differential capacitance curves for n‐dodecyl‐and n‐hexadecyltrimethylammonium bromides in N‐potassium chloride were generally similar to those in N‐sulphuric acid, and the calculated surface concentrations of the adsorbed quaternary ammonium ions were almost the same. The wider range of potential in the present experiments enabled the desorption peaks in the differential capacitance curves for the more dilute solutions to be demonstrated. The stronger solutions gave subsidiary peaks, or steps, which may be associated with the formation of double or multiple layers. The results of these and previous experiments are explained on the basis that the adsorbed layer of n‐alkyltrimethylammonium ions does not completely exclude solvated ions, but hinders their approach to the metal surface.