Speeds of sound and isentropic compressibilities of (n-alkoxyethanols plus toluene) at T=298.15 K

Speeds of sound u at the temperature 298.15 K for six (n-alkoxyethanol + toluene) were measured over the whole composition range. The n-alkoxyethanols were 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol, and 2-(2-butoxyethoxy)ethanol. Excess molar volumes V-m(E) at T = 298.15 K were also measured for the mixtures of toluene and 2-methoxyethanol, 2-ethoxyethanol, or 2-butoxyethanol over the whole composition range. The speed of sound values were combined with excess molar volumes to obtain values for the product K-S,K-m of the molar volume and the isentropic compressibility kappa(S), and the corresponding excess quantities K-S,m(E) were also calculated. The K-S,m(E) curves are sigmoid for all S,m mixtures. The deviations of the speeds of sound u(D) from their values u(id) in an ideal mixture were obtained for all measured mole fractions. These values are compared with the mixing function deltau calculated in the paper. The behaviour of u, u(D), deltau, and K-S,m(E) as a function of composition and number of carbon atoms in the aliphatic chain of the alkoxyethanol is discussed. Also, theoretical values of the molar isentropic compressibility K-S,K-m and speed of sound u were calculated using the Prigogine-Flory-Patterson theory with a van der Waals potential energy model and the results compared with experimental data. (C) 2002 Elsevier Science Ltd. All rights reserved.