Viscosities of aqueous solutions of dimethylsulfoxide, 1,4-dioxane and tetrarydrofuran

Viscosities of the systems, water(W)+dimethylsulfoxide(DMSO), W+1,4-dioxane (DXN) and W+tetrahydrofuran(THF), are measured at temperatures ranging fro m 303.15 - 323.15 K. Viscosities and excess viscosities are plotted against the mole fraction of the organic solutes. On addition of solutes to water, viscosities first increase rapidly, pass through maxima and then decline c ontinuously until the pure state of solutes is reached. Excess viscosities are found to be positive and large in magnitude and their curves are simila r to those of the viscosity curves. The ascending part of the viscosity cur ves in the water-rich region is accounted for by both the hydrophobic effec t of forming cage structures around solutes and the hydrophilic effect form ing H-bonds between water and organic solutes. The descending part of the v iscosity curves is explained by the continuous destruction of cages formed. The maxima are thought to be due to competing processes of formation and d estruction of cage structures.