Title: soap
Long Title: IUPAC Gold Book - soap
DOI: 10.1351/goldbook.S05721
Status: current

Definition
A salt of a fatty acid, saturated or unsaturated, containing at least eight carbon atoms or a mixture of such salts. A neat soap is a lamellar structure containing much (e.g. $\pu{75\%}$) soap and little (e.g. $\pu{25\%}$) water.

Related Term
- salt: https://goldbook.iupac.org//terms/view/S05447

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

Other Outputs
- html: https://goldbook.iupac.org/terms/view/S05721/html
- json: https://goldbook.iupac.org/terms/view/S05721/json
- xml: https://goldbook.iupac.org/terms/view/S05721/xml

Citation: Citation: 'soap' 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.S05721
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Accessed: 2026-07-23T07:59:17+00:00