Or. Carre et al., SPECTROFLUOROMETRIC MEASUREMENTS OF LOCAL COMPOSITIONS AND COMPARISONTO THERMODYNAMIC MODELS, Industrial & engineering chemistry research, 33(5), 1994, pp. 1355-1362
We present measurements of the local composition about the fluorescenc
e probes pyrene and benzo[ghi]perylene in binary liquid solvents. The
probes provide information about the solvation of the solute on a micr
oscopic scale. The advantage of the fluorescence probes is that they a
re relatively nonpolar and do not contain functional groups with which
to form hydrogen bonds. Actual measurement of local compositions is i
mportant as the concept is the basis of a number of useful thermodynam
ic models. Thus, we compare the measured values with those predicted f
rom both the nonrandom two-liquid (NRTL) equation and the Wilson equat
ion. The standard recommended values of the nonrandomness factor in th
e NRTL equation generally underestimate the magnitude of the local com
positions. Larger nonrandomness factors provide better descriptions of
the microscopic environment. On the other hand, the Wilson equation o
verestimates the magnitude of the local compositions in all cases.