WETTING AND SOLUTE ADSORPTION FOR PARAFFIN-AQUEOUS SODIUM STEARATE SYSTEM

The wettability of a paraffin surface by an aqueous solution of sodium stearate has been related to the adsorption of sodium stearate onto the solid surface. The contact angle (θ) and the amount of solute adsorption (Γ) at the solid/liquid interface were measured as a function of time for the compact paraffin surface together with the surface tensions of the wetting solutions (σl) and water (σw). A linear relationship was confirmed to hold between σl (1 + cos θ/(θl + σw) and Γi calculated from equilibrium data. The corresponding plots for nonequilibrium data fall near this straight line. The linear relationship is explained by generalizing the Doss and Bartell theories of wetting and by taking into account the fact that the work of adhesion of a solute against a solid surface is affected by the solute retention ΔS on the solid surface. © 1997 Elsevier Science Ltd. All rights reserved.