{"term":{"id":"15377","title":"Ostwald coefficient","longtitle":"IUPAC Gold Book - Ostwald coefficient","doi":"10.1351\/goldbook.15377","code":"15377","status":"current","definitions":[{"id":1,"text":"Volume \\(V^{\\rm{g}}\\) of an amount \\(n_{\\ce{B}}^{\\rm{l}}\\) of a dissolved gas calculated at given temperature \\(T\\) and pressure \\(p\\) divided by the volume of the dissolving liquid of volume \\(V^{\\rm{l}}\\) and containing an amount \\(n_{\\ce{A}}\\) of solvent at the same temperature \\(T\\) and pressure \\(p\\).","notes":{"1":"There are two Ostwald coefficients, depending on whether the liquid is the equilibrium solution or the pure liquid, with mathematical definitions:Ostwald coefficient, solution reference \\[L_{\\ce{B}} = V^{\\rm{g}}(T,p,n_{\\ce{B}}^{\\rm{l}})\/V^{\\rm{l}}(T,p,n_{\\ce{A}}, n_{\\ce{B}}^{\\rm{l}}) = c_{\\ce{B}}^{\\rm{l}}\/c_{\\ce{B}}^{\\rm{g}}\\] Ostwald coefficient, pure solvent reference \\[L_{\\ce{B}}^{\\ast} = V^{\\rm{g}}(T,p,n_{\\ce{B}}^{\\rm{l}})\/V^{\\rm{l}}(T,p,n_{\\ce{A}})\\]","2":"The relations between the molality \\(m_{\\ce{B}}(p)\\) or mole fraction \\(x_{\\ce{B}}(p)\\) of dissolved gas and the Ostwald coefficients are \\[\\begin{array}{l} \\frac{1}{x_{\\ce{B}}(p)} = 1 + \\frac{1}{m_{\\ce{B}}(p)M_{\\ce{A}}} = 1 + \\frac{RTZ_{\\ce{B}}}{V_{\\ce{A}}p_{\\ce{B}}L_{\\ce{B}}} \\\\ \\frac{1}{x_{\\ce{B}}(p)} = 1 + \\frac{1}{m_{\\ce{B}}(p)M_{\\ce{A}}} = 1 + \\frac{RTZ}{pV_{m,\\ce{A}}L_{\\ce{B}}^{\\ast}} \\end{array}\\] where \\(V_{\\ce{A}}\\), \\(V_{m,\\ce{A}}\\) are the respective partial molar volume and molar volume of the solvent and \\(Z_{\\ce{B}}\\) is the compression factor of the gas.","3":"The Ostwald coefficient and the related quantities for expression of gas solubility, the absorption, Bunsen, and Kuenen coefficients, appear frequently in the older literature of gas solubility determination. However, the modern practice, recommended here, is to express gas solubility as molality, mole fraction, or mole ratio."},"links":[{"term":"Bunsen","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/15317"},{"term":"Kuenen coefficients","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/15374"},{"term":"mole fraction","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/15376"},{"term":"mole ratio","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/15341"}],"sources":["PAC, 2008, 80, 233. 'Glossary of terms related to solubility (IUPAC Recommendations 2008)' on page 256 (https:\/\/doi.org\/10.1351\/pac200880020233)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/15377\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/15377\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/15377\/plain"},"citation":"Citation: 'Ostwald coefficient' 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.15377","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":"2026-07-28T11:16:06+00:00"}}