https://doi.org/10.1351/goldbook.O04342
Quantity characterizing the @[email protected] of the @[email protected] from ideal behaviour referenced to @[email protected] The osmotic @[email protected] on a molality basis is defined by: \[\phi =\frac{\mu _{\text{A}}^{*}- \mu _{\text{A}}}{R\ T\ M_{\text{A}}\ \sum _{\begin{array}{c}
i
\end{array}}m_{i}}\] and on an amount fraction basis by: \[\phi =\frac{\mu _{\text{A}}^{*}- \mu _{\text{A}}}{R\ T\ \ln x_{\text{A}}}\] where \(\mu _{\text{A}}^{*}\) and \(\mu _{\text{A}}\) are the chemical potentials of the solvent as a pure substance and in solution, respectively, \(M_{\text{A}}\) is its molar mass, \(x_{\text{A}}\) its amount fraction, \(R\) the @[email protected] and \(T\) the temperaure. The latter osmotic @[email protected] is sometimes called the rational osmotic @[email protected]