Title: miscibility gap
Long Title: IUPAC Gold Book - miscibility gap
DOI: 10.1351/goldbook.MT07270
Status: current

Definition
Area within the coexistence curve of an isobaric phase diagram (temperature vs composition) or an isothermal phase diagram (pressure vs composition).

Note
A miscibility gap is observed at temperatures below an upper critical solution temperature (UCST) or above the lower critical solution temperature (LCST). Its location depends on pressure. In the miscibility gap, there are at least two phases coexisting.

Related Terms
- critical solution temperature: https://goldbook.iupac.org//terms/view/C01401
- miscibility: https://goldbook.iupac.org//terms/view/MT07230
- upper critical solution temperature: https://goldbook.iupac.org//terms/view/UT07280

Source
- PAC, 2004, 76, 1985. 'Definition of terms related to polymer blends, composites, and multiphase polymeric materials (IUPAC Recommendations 2004)' on page 1996 (https://doi.org/10.1351/pac200476111985)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/MT07270/html
- json: https://goldbook.iupac.org/terms/view/MT07270/json
- xml: https://goldbook.iupac.org/terms/view/MT07270/xml

Citation: Citation: 'miscibility gap' 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.MT07270
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Accessed: 2026-06-04T09:32:14+00:00