Dynamic contact angles. Part VI. The mechanism of spreading in a liquid–solution–solid system

Abstract

Surface-tension changes at the liquid–solution interface due to compression have been calculated by two methods for drops of carbon tetrachloride spreading over a resin (CR39) surface in solutions of sodium n-octyl sulphate. It is concluded that when a drop makes contact with the resin, solute molecules in the base of the drop are compressed into the remaining liquid–solution interface and thereafter are rapidly desorbed. Calculations have been made on the changes in the potential energy of the drop and on the surface-energy changes due to compression of the solution–solid interface. Lack of agreement indicates that Young's equation does not apply to a dynamic system unless other factors account for the energy difference.