THERMOCHEMICAL INVESTIGATIONS OF ASSOCIATED SOLUTIONS .16. COMPARISON OF THE EXTENDED NIBS MODEL AND MOBILE ORDER THEORY FOR SOLUBILITY IN SYSTEMS CONTAINING SOLUTE-SOLVENT COMPLEXATION

A relatively simple equation is derived from mobile order theory for calculating solute-solvent association constants from measured solubility data in binary solvent mixtures. The newly derived expression was found to describe carbazole solubilities in nine binary dibutyl ether + alkane solvent mixtures to within an average absolute deviation of 2.5% using a single association constant. The association constant varied slightly with inert hydrocarbon cosolvent, with the numerical values ranging from a lower limit of K-AC = 1400 for n-heptane to an upper Value of K-AC = 1955 for isooctane.