On the Location of the Forces

The electrical double layer surrounding solid particles suspended in water is assumed to be due to a difference in the concentration of the oppositely charged ions of an electrolyte in the enveloping film (i.e. the film of water which adheres to and moves with the particle in an electrical field) and the opposite film. This difference in concentration is generally ascribed to a preferential adsorption of one kind of a pair of oppositely charged ions by the suspended particle. Such a definition is inadequate inasmuch as the term adsorption includes two entirely different kinds of forces; namely, first, forces inherent exclusively in the water, and second, forces of attraction between the suspended particle and the adsorbed ions. Forces inherent exclusively in the water are responsible for the cataphoretic migration of gas bubbles in water in which the gas bubbles are negatively charged since the nature of the gas is of no influence on the P.D. McTaggart~ suggested that in this case there exists an excess of OH ions in the film of water which envelops the gas bubble (adhering to and moving with it) ; while the opposite film has an equal excess of H ions. The writer has recently suggested that this electrical double layer might be due to an orientation of the molecules of water at the surface of the water whereby the oxygen atoms of the water molecules are turned outwards and the two hydrogen atoms or ions are turned inside into the watery Such an orientation of the molecules of water at the free surface might also explain the well known fact that the