The unusual coexistence curve of 2-butanol + water. An experimental and theoretical study

Abstract

The coexistence curve of the 2-butanol + water system has been measured at P ≈ 1 bar, with a higher precision and a more detailed description of the pinch-off region than in previous experimental studies. The data points in the vicinity of the UCST have been fitted to a simple scaling expression to obtain the critical point coordinates and an estimation of the range of validity of simple scaling. The experimental binodal has been used to test two Ising-like models including directional interactions: an asymmetric decorated lattice one and a lattice-gas model with fluctuating orientational degrees of freedom. Both models offered comparable results when a symmetrized composition variable was used.