work of adhesion

Also contains definition of: work of separation

The work of adhesion per unit area, w A α β δ, is the work done on the system when two condensed phases α and β, forming an interface of unit area are separated reversibly to form unit areas of each of the αδ- and βδ- interfaces.
w A α β δ = γ α δ + γ β δ − γ α β
where γ α β, γ α δ and γ β δ are the surface tensions between two bulk phases α, β; α, δ and β, δ respectively. The work of adhesion as defined above, and traditionally used, may be called the work of separation.
Source:
PAC, 1972, 31, 577 (Manual of Symbols and Terminology for Physicochemical Quantities and Units, Appendix II: Definitions, Terminology and Symbols in Colloid and Surface Chemistry) on page 597