https://doi.org/10.1351/goldbook.15322
Index in the basic equation describing a coexistence curve \[\beta = \lim \limits_{T \to T_{\rm{c}}} \left(\frac{\partial \ln (x'' - x')}{\partial \ln \vert T - T_{\rm{c}}\vert} \right)\] where \(x''\), \(x'\) are the mole fractions of one component in the respective concentrated and dilute phases and \(T_{\rm{c}}\) is the critical solution temperature.