Excess molar volumes and ultrasonic speeds of diethylene glycol monomethyl ether : N-alcohol mixtures at 298.15K

Excess molar volumes V m E and ultrasonic speed u have been measured at 298.15K in binary mixtures of diethylene glycol monomethyl ether with methanol, ethanol, 1-propanol, 1-pentanol and 1-hexanol over the entire composition range. The V m E values were found to be negative for methanol and ethanol, and to change sign for propanol, with positive V m E values at higher mole fraction of diethylene glycol monomethyl ether. They were positive for 1-pentanol and 1-hexanol with diethylene glycol monomethyl ether over the whole composition range. The values increased with increase in chain length of the n-alcohol. The results have been used to estimate the excess partial molar volumes V m,i E of the components, and they have also been analysed using the Prigogine-Flory-Patterson (PFP) theory. An analysis of each of the three contributions - interactional, free volume and P*- shows that the free volume effect and the P* contribution are negative for all the mixtures, whereas the interactional contribution is negative only for methanol. The isentropic compressibilities k S and their excess values k S E were found to vary in the order methanol < ethanol < 1-propanol < 1-pentanol < 1-hexanol. The behaviour of V m E , V m,i E , X 12 (Flory's interaction parameter) κ S E and Au with composition and the number of carbon atoms in the alcohol molecule is discussed.