Effect of Potassium Bromide on the Volumetric Behaviour of Binary Mixtures of Ethylene and Propylene Glycols with Methanol

Abstract

The effect of potassium bromide (KBr) on the volumetric properties of
binary mixtures of ethylene and propylene glycols with methanol has
been studied using experimental density values of the mixtures and
pure component solvents at varying compositions (0.1, 0.3, 0.5, 0.7
and 0.9) of the glycols and concentrations (0.01, 0.03, 0.07, 0.09 M)
of KBr, at 298 K. The data obtained were used to compute the excess
molar volumes (VE
) of the binary mixtures at the various compositions
and concentrations. The results show that the VE
values of all the
binary mixed systems were negative over the entire range of solvent
compositions and concentrations of KBr investigated except at 0.7 and
0.9 compositions of propylene glycol mixtures with positive values of
V
E
. The magnitude of the negative excess molar volumes gradually
increased with composition of the glycol and concentration of ethylene
glycol to a maximum, beyond which the values steadily decreased. For
propylene glycol mixtures, excess molar volumes became less negative
as the concentration of KBr increased. These observations have been
discussed on the basis of molecular interactions due to structural
differences between the binary mixed solvents.