Concentration of Stearic Acid in Monolayers Adsorbed from Solution

Abstract

MATHIESON¹ has recently obtained electron micrographs of oleophobic stearic acid films adsorbed on mica from hexadecane solution. These show islands of stearic acid in the monolayer, with only about one-third of the surface covered. The observations are in good agreement with the results reported by Cook and Ries² for the adsorption of radioactive stearic acid on mica and gold from hexadecane solutions. They, too, found that only 20–30 per cent of a close-packed monolayer of stearic acid molecules was adsorbed on these inert substrates. Mathieson also points out that island structures are not formed when adsorption of stearic acid proceeds from the melt. These authors have interpreted their observations in terms of a solvent-solute interaction whereby stearic acid molecules adsorbed from solution are surrounded by hexadecane molecules in an oriented array.