A study of the refractive index and surface tension synergy of the binary water/ethanol: influence of concentration

Pure alcohols or alcohols mixed with water are the most widely used solvents in a great variety of industrial applications, including the formulation of pharmaceutical and cosmetic products. As a result of water/alcohol molecular associations, variations result in the physico-chemical characteristics of the system, such as density, viscosity, refractive index and surface tension. The present study investigates the refractive index and the surface tension of ethanol and water mixtures at a temperature of 25degreesC, for different molar fractions. The data obtained allow us to study the corresponding refractive index and the surface tension synergies; in this sense, an absolute maximum refractive index is recorded for a molar fraction of 0.667, while maximum synergy (both absolute and relative) is observed for a molar fraction 0.333. As regards surface tension, minimum absolute and relative synergy is recorded for molar fraction 0.2, since synergy is negative for the surface tensions of the mixtures. Determinations are also made of the molar refraction of the mixtures and of the variation in refractive indices with temperature.