Analysis of the structure of aqueous solutions of isopropanol based on optical, volumetric, and elastic data

The curve of the concentration dependence of the total molecular light scattering coefficient of x C 3 H 7 OH-(1 − x )H 2 O solutions showed two sharp maxima (at x = 0.04 and 0.09) and a minimum at x = 0.06 mole fractions, suggesting a considerable rearrangement of the structure of the solutions near these concentrations. The concentration dependences of excess molar volume, adiabatic compressibility, and molar refraction showed negative deviations from the ideal with a minimum in the range x = 0.18–0.3. The structure of water was assumed to undergo a rearrangement at x = 0.04 accompanied by structural fluctuations, which dispersed at 0.04 < x < 0.06. At x = 0.06, associates of isopropanol molecules started to form, whose number and size increased linearly up to x = 0.13. In the 0.13 < x < 0.35 concentration range, some kind of an aqueous alcohol emulsion containing pure alcohol “nanodrops” formed and the solutions became microheterogeneous.