Creeping-film phenomenon of potassium chloride solution

Abstract

A PECULIAR creeping film that is similar to the superfilm of liquid helium II, but which occurs at room temperatures and has a much lower transfer rate, takes place in saturated potassium chloride aqueous solution. In an electrolytic experiment using saturated KCl solution as the salt bridge, we noticed that without any disturbance the solution could not be kept in the beaker all the time. A thin surface film creeps up the beaker wall very slowly, about several centimetres a day, flows out over the brim and then down the outside surface of the beaker. Creeping can also be observed up the surface of the electrode and the salt bridge tube (Fig. 1). On surfaces over which the film has crept, potassium chloride crystals form as the water in which KCl is dissolved evaporates. Within a few days the solution in the beaker drains out completely and the entire surface of the beaker becomes covered with a thin layer of potassium chloride crystals, about 10⁻² cm thick.