“…Efforts in this area have included correlation of refractive index with density, 1,2 surface tension [3][4][5] and dielectric permittivity, 6,7 the use of n to calculate the molecular composition of hydrogen-bonded complexes, 8,9 and, in particular, the use of several well-known mixing rules 1 for n that allow more or less accurate prediction [10][11][12] of excess molar volume V m E (or, vice versa, the prediction of n from density data). 13,14 Refractive index and V m E data are in fact often reported together [15][16][17][18][19][20] even though, surprisingly, it is unusual to interrelate them for discussion of results. Given the above-mentioned rules, deviation of n from ideality would be expected to correlate well with V m E and to be physically interpretable itself.…”