THERMOCHEMICAL INVESTIGATIONS OF ASSOCIATED SOLUTIONS .16. COMPARISONOF 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 c alculating solute-solvent association constants from measured solubili ty data in binary solvent mixtures. The newly derived expression was f ound 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 varie d slightly with inert hydrocarbon cosolvent, with the numerical values ranging from a lower limit of K-AC = 1400 for n-heptane to an upper V alue of K-AC = 1955 for isooctane.