Mathematical Representation of Thermodynamic Properties. Carbazole Solubilities in Binary Alkane + Dibutyl Ether and Alkane + Tetrahydropyran Solvent Mixtures

Experimental solubilities are reported for carbazole dissolved in binary mixtures containing tetrahydropyran with n-hexane, n-heptane, clyclohexane, isooctane, n-hexadecane and t-butylcyclohexane at 25°C. Results of these measurements, along with published carbazole solubilities in ten alkane + dibutyl ether mixtures, are used to test two mathematical representations based upon the combined Nearly Ideal Binary Solvent (NIBS)/Redlich-Kister equations and Modified Wilson model. For the systems studied, the Modified Wilson equation is found to be the better two-parameter mathematical representation with deviations between experimental and back-calculated values being on the order of ± 3% or less. The NIBS/Redlich-Kister representation requires up to four adjustable "curve-fit" parameters to describe the solubility data.