Chemical potential and concentration fluctuation in some aqueous alkane-mono-ols at 25°C

Vapour pressures of binary aqueous solutions of methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 1-hexanol were measured at 25.00(o)C in small compositional increments over the entire compositional range. Without resorting to any fitting function, the partial pressures were calculated numerically by methods based on the Gibbs-Duhem relation. When the system had an azeotrope, near which the numerical methods caused large errors, a graphical readjustment was applied such that the concentration fluctuation, S-XX(0) = RT(1 - x(AL))/(partial derivativemu (E)(AL)/partial derivativex(AL)), connected smoothly across the azeotrope. Values of S-XX(0) from scattering experiments were also used as a guide for the readjustment procedure. Hence, we report here chemical potential data free from any model or any fitting function.