ABSTRACT
The expression 'double layer' is something of a misnomer and arose from the original simple view of an organized arrangement of positive ions from solution, to compensate for the negative charges in the surface, to form an interfacial region similar to a parallel plate condenser. Although double layers are general interfacial phenomena, some attention will be paid here to electrodeelectrolyte interfaces because of their importance in electrode kinetics. Further, the theory leads to a proper interpretation of electrokinetic phenomena, to an understanding of the factors affecting colloid stability and to the elucidation of cell membrane and ion-exchange processes. The line drawn through the centre of such ions at this distance of closest approach marks a boundary known as the 'outer Helmholtz plane'. Interfacial tension measurements on liquid metal electrodes, such as mercury, have provided a great deal of information about double layer structure and have indicated the factors governing adsorption at a charged interface.
