Available in paperback for the first time, this is a complete examination of the molecular origins of surface phenomena. Comprehensive in scope, the book traces the history of ideas in this area and presents a detailed discussion of modern theories and an assessment of their present state. The treatise emphasizes the liquid-gas surface, but includes two authoritative chapters of liquid-liquid surfaces. Now thoroughly revised, this text includes the latest information on important developments that have occurred in recent years. Handy cross referencing makes the volume easily accessible and of particular value to theorists and industrial scientists who need to understand or predict the properties of interfaces in fluid-phase equilibria.