Speeds of sound and isentropic compressibilities of diethylene glycol dimethyl ether - n-Alcohol mixtures at 298.15 K

The speeds of sound has been obtained at a frequency of 4 MHz in diethylene glycol dimethyl ether + methanol, + ethanol, + 1-butanol, and + 1-pentanol across the entire composition range, at the temperature 298.15 K and atmospheric pressure using a NUSONIC velocimeter based on the sing-around technique. The ultrasonic speed values have been combined with those of the excess molar volumes converted to densities to obtain estimates of the product K-S,K-m of the molar volumes and isentropic compressibility kappa (S), and excess quantity K-S,m(E). The K-S,m(E) values are negative over the entire range of composition for all mixtures with the exception of 1-pentanol, which changes sign from positive to negative. The magnitude of K-S,m(E) increase with the number of carbon atoms in the n-alcohol. The deviations of the speeds of sound u(D) from their ideal values u(id) in an ideal mixture were also calculated for all measured mole fractions. The behaviour of u, u(D), and K-S,m(E) with composition and the number of carbon atoms in the alcohol molecule is discussed.