The streaming maxima, which often appear in current–potential curves obtained at mercury (Hg) electrodes, e.g., dropping Hg electrode (DME) and hanging Hg drop electrode (HMDE), have been categorized into three types (i.e., maxima of the first, second and third kinds) and explained in the excellent review [1]. The factors governing the streaming maxima are the difference between the values of surface tension (γ) at the bottom and the neck of Hg drop that usually occurs at DME and HMDE, tangential flow of Hg at the surface of Hg drop owing to nonradial drop-growth of DME and nonuniform adsorption of certain surface-active substances on electrode surface