Title: Henry’s law solubility constant (via b and p)
Long Title: IUPAC Gold Book - Henry’s law solubility constant (via b and p)
DOI: 10.1351/goldbook.09026
Status: current

Definition
Molality \(b\) of a species divided by the partial pressure \(p\) of that species in the gas phase under equilibrium conditions at infinite dilution: \[H_{\rm{s}}^{bp}: = \underset{b \to 0}{\rm{lim}}\frac{b}{p}\]

Notes
1) The coherent SI unit for \(H_{\rm{s}}^{bp}\) is \(\pu{mol m-3 Pa-1}\).
2) Here, the symbol \(b\) is used for molality (instead of \(m\)) to avoid confusion with the symbol \(m\) for mass.
3) Molality refers to the mass of solvent and should not be confused with content which refers to the mass of solution.

Example
The Henry solubility of ozone in water at \(T = \pu{298.15 K}\) is \(H_{\rm{s}}^{bp}(\ce{O3}) = \pu{1.0E-7 mol kg-1 Pa-1}\).

Related Term
- Henry’s law solubility constant: https://goldbook.iupac.org//terms/view/09021

Source
- PAC, 2022, 94, 71. 'Henry’s law constants (IUPAC Recommendations 2021)' on page 76 (https://doi.org/10.1515/pac-2020-0302)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/09026/html
- json: https://goldbook.iupac.org/terms/view/09026/json
- xml: https://goldbook.iupac.org/terms/view/09026/xml

Citation: Citation: 'Henry’s law solubility constant (via b and p)' 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.09026
License: The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms.
Collection: If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .
Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.
Accessed: 2026-04-27T16:12:57+00:00