JOURNAL of the Tunisian Chemical Society

In this work we experimentally studied the variation of partial molal volumes and partial molal enthalpies of mixture of water and dioxane with the molar fraction. X_D of dioxane at T = 298°K and P = 1 atm. We also studied the liquid-vapor diagram in order to determine the variation of activity coefficients of water and dioxane with X_D. It has been found that : i) Partial molal volumes remain constant at low X_D ; ii) The enthalpy of mixture varies in «S» and is equal to zero for X_D = 0.46; iii) The liquid-vapor diagram presents an azeotrope for T = 385.5°K and X_D = 0.5; iv) Activity coefficients are linear to T-1 . These results are interpreted as follows : A molecule of dioxane locks into the hexagonal hydrogen bond network of water so that the volume effects remain weak. At low X_D each dioxane molecule is surrounded by 8 water molecules. The water-dioxane interaction has a H bound character. For X_D < 0.5 the solution is quasi-regular and the deviation from the regularity is due to the dioxane-dioxane interaction. Note that our conclusions concerning water-dioxane mixtures agree with some recent structural studies.

J. M’Halla, R. Besbes, S. M’Halla

1,4 dioxane, water, enthalpy, density, azeotrope, regular, structure

Pages 1303-1315