Dj. Phillips et Jf. Brennecke, SPECTROSCOPIC MEASUREMENT OF LOCAL COMPOSITIONS IN BINARY-LIQUID SOLVENTS AND COMPARISON TO THE NRTL EQUATION, Industrial & engineering chemistry research, 32(5), 1993, pp. 943-951
In this paper we compare the local compositions of solvents around a s
olute predicted from the nonrandom two-liquid (NRTL) equation with exp
erimental spectroscopic measurements of the local compositions to test
the ability of the thermodynamic equation to model the true local env
ironment. Shifts in the wavelength of maximum absorption of the solvat
ochromic probe phenol blue are used to estimate the local compositions
. Mixtures investigated include acetone/cyclohexane, triethylamine/cyc
lohexane, ethyl butyrate/cyclohexane, cyclohexanone/cyclohexane, tolue
ne/cyclohexane, acetophenone/cyclohexane, acetophenone/toluene, and et
hyl butyrate/cyclohexanone. Comparison with the NRTL equation requires
the interaction energies between the phenol blue and each of the solv
ents, and these parameters are determined from the solubility of pheno
l blue in the pure solvents. In most cases the measured local composit
ions compare reasonably well with those predicted from the NRTL equati
on. Spectroscopic measurements such as these are very useful in testin
g and refining thermodynamic models.