Title: Gibbs adsorption
Long Title: IUPAC Gold Book - Gibbs adsorption
DOI: 10.1351/goldbook.G02627
Status: current

Definition
The surface excess amount or Gibbs adsorption of component \(i\), \(n_{i}^{\sigma }\), which may be positive or negative, is defined as the excess of the amount of this component actually present in the system over that present in a reference system of the same volume as the real system and in which the bulk concentrations in the two phases remain uniform up to the Gibbs dividing surface. That is \[n_{i}^{\sigma }=n_{i}- V^{\alpha }\ c_{i}^{\alpha }- V^{\beta }\ c_{i}^{\beta }\] where \(n_{i}\) is the total amount of the component \(i\) in the system, \(c_{i}^{\alpha }\) and \(c_{i}^{\beta }\) are the concentrations in the two bulk phases \(\alpha \) and \(\beta \), and \(V^{\alpha }\) and \(V^{\beta }\) are the volumes of the two phases defined by the Gibbs surface.

Related Terms
- Gibbs surface: https://goldbook.iupac.org//terms/view/G02635
- surface excess: https://goldbook.iupac.org//terms/view/S06171

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 588 (https://doi.org/10.1351/pac197231040577)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/G02627/html
- json: https://goldbook.iupac.org/terms/view/G02627/json
- xml: https://goldbook.iupac.org/terms/view/G02627/xml

Citation: Citation: 'Gibbs adsorption' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.G02627
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Accessed: 2026-04-21T12:27:47+00:00