Title: Donnan equilibrium
Long Title: IUPAC Gold Book - Donnan equilibrium
DOI: 10.1351/goldbook.D01831
Status: current

Definition
The equilibrium characterized by an unequal distribution of diffusible ions between two ionic solutions (one or both of the solutions may be gelled) separated by a membrane which is impermeable to at least one of the ionic species present, e.g. because they are too large to pass through the pores of the membrane. The membrane may be replaced by other kinds of restraint, such as gelation, the field of gravity, etc., which prevent some ionic components from moving from one phase to the other, but allow other components to do so.

Related Terms
- gelation: https://goldbook.iupac.org//terms/view/GT07621
- membrane: https://goldbook.iupac.org//terms/view/MT06878

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

Other Outputs
- html: https://goldbook.iupac.org/terms/view/D01831/html
- json: https://goldbook.iupac.org/terms/view/D01831/json
- xml: https://goldbook.iupac.org/terms/view/D01831/xml

Citation: Citation: 'Donnan equilibrium' 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.D01831
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Accessed: 2026-07-23T20:55:52+00:00