were close to the theoretical values. Thus, the relationship between ΔnD 20 and xdic followed a similar pattern as the dependence of the excess molar volume (Vm E20 ) on the molar fraction of dicamba. This finding corroborates the known relationship between the density and refractive index: with a higher density of a substance, the spatial packing of its chemical constituents increases, and refraction results from the interaction of light with molecules (or ions) .