Viscosities and excess viscosities of methanol, ethanol and<i>n</i>-propanol in pure water and in water + surf excel solutions at different temperatures

Abstract

Viscosities, η of the systems methanol, ethanol and n-propanol in water, and in 0.05% and 0.1% Surf Excel (SE) solutions were measured at temperatures 303.15, 308.15, 313.15, 318.15 and 323.15 K, respectively, covering the whole composition range. On addition of alcohols to water or water + SE systems, viscosities pass through the maxima and then decline continuously. The heights of the maxima occurring between 0.2 and 0.3 mole fraction of alcohols are in the order n-propanol>ethanol>methanol. Excess viscosities, ηE for the systems were found to be positive. For all alcohols, excess viscosities show a maxima in the water-rich region. All these properties have been expressed satisfactorily by appropriate polynomials. No appreciable change in the viscosities and excess viscosities were observed by the addition of surfactant (0.05% and 0.1%) to the studied systems. An explanation of ηE in terms of hydrophobic hydration and hydrophilic effect of the solutes is offered.