Chapter Four - Determination of Interfacial Tensions between Water and Other Condensed-Phase Materials

Abstract

Publisher Summary This chapter discusses the determination of interfacial tensions between water and other condensed-phase materials. The interfacial tension ( γ SL ) between a solid (S) (or other condensed-phase material) and a liquid (L) is a term of prime importance as a part of all versions of the Dupre equations that govern the interaction energies between condensed-phase materials and the liquid in which they are immersed. Apolar organic liquids are the only organic liquids whose (molecular) interfacial tensions with water still are correctly measurable via drop-shape or drop-weight methods. The measurement of interfacial tensions between water-immiscible liquids and water by means of drop-shape or drop-weight determinations is a popular approach for determining “oil–water” interfacial tensions. When using drop-shape or drop-weight methods with polar organic compounds, from the very moment such polar liquids are immersed in water only those molecules that actually dissolve in the water remain suspended as single, separate molecules that have their polar as well as their apolar moieties freely exposed to the water on all sides, via their water-interfaces. It is only with apolar organic liquids that one will find that γ iw 0 determined via their aqueous solubility or measured via drop-shape or drop-weight approaches gives identical results. With polar organic liquids drop-shape or drop-weight methods should not be used.