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. \[w_{\text{A}}^{\unicode[Times]{x3B1} \unicode[Times]{x3B2} \unicode[Times]{x3B4} }=\gamma ^{\unicode[Times]{x3B1} \unicode[Times]{x3B4} }+\gamma ^{\unicode[Times]{x3B2} \unicode[Times]{x3B4} }- \gamma ^{\unicode[Times]{x3B1} \unicode[Times]{x3B2} }\] 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.
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 (