A Study of the Interaction between the Stearic Acid Monolayer and the Calcium Ions by the Radiotracer Method

Abstract Direct measurement by the radiotracer method has been carried out in order to determine the surface excess of calcium on the stearic acid monolayer. It did not provoke any disturbance in the monolayer, such as “skimming off” or “building up”. At higher pH values the stearic acid monolayer spread on a calcium chloride solution shows a very remarkable inhomogeneity. It has been pointed out that this inhomogeneity must be taken into consideration in determining the composition of the monolayer. The mixed monolayer of stearic acid and calcium stearate satisfies the equation derived by assuming this monolayer to be a mixture not athermal.