Title: thickness of electrical double layer
Long Title: IUPAC Gold Book - thickness of electrical double layer
DOI: 10.1351/goldbook.T06343
Status: current

Definition
The length characterizing the decrease with distance of the potential in the double layer = characteristic Debye length in the corresponding electrolyte solution = \(\kappa^{-1}\):\[\frac{1}{\kappa } = \sqrt{\frac{\varepsilon_{\rm{r}}\varepsilon_{0}RT}{F^{2}\sum _{i}c_{i}z_{i}^{2} }}\]  \[\frac{1}{\kappa } = \sqrt{\frac{\varepsilon_{\rm{r}}RT}{4\pi F^{2}\sum _{i}c_{i}z_{i}^{2} }}\](rationalized four-quantity system)  (three-quantity electrostatic system) where \(\varepsilon\) = static permittivity = \(\varepsilon_{\rm{r}}\varepsilon_{0}\), \(\varepsilon_{\rm{r}}\) = relative static permittivity of solution; \(\varepsilon_{0}\) = permittivity of vacuum, \(R\) = gas constant, \(T\) = thermodynamic temperature, \(F\) = Faraday constant, \(z_{\rm{i}}\) = concentration of species \(i\), \(z_{\rm{i}}\) = ionic charge on species \(i\).

Related Terms
- Debye: https://goldbook.iupac.org/terms/view/D01533
- Faraday constant: https://goldbook.iupac.org/terms/view/F02325
- gas constant: https://goldbook.iupac.org/terms/view/G02579
- permittivity: https://goldbook.iupac.org/terms/view/P04507
- permittivity of vacuum: https://goldbook.iupac.org/terms/view/P04508
- thermodynamic temperature: https://goldbook.iupac.org/terms/view/T06321

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/T06343/html
- json: https://goldbook.iupac.org/terms/view/T06343/json
- xml: https://goldbook.iupac.org/terms/view/T06343/xml

Citation: Citation: 'thickness of electrical double layer' 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.T06343
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Accessed: 2026-08-09T14:32:43+00:00