Speeds of sound and isentropic compressibilities of ethylene glycol dimethyl ether-n-alcohol mixtures at 298.15 K

The speeds of sound u have been measured at 298.15 K in binary mixtures of ethylene glycol dimethyl ether with methanol, ethanol, 1-butanol, and 1-pen tanol over the entire composition range using a NUSONIC velocimeter based o n the sing-around technique. Their values have been combined with those of densities derived from excess molar volumes to obtain estimates of the prod uct K-S,K-m of the molar volumes and isentropic compressibility kappa (s), and their excess values K-S,m(E). The K-S,m(E) values are shown to be negat ive for all mixtures over the entire composition range. The values increase d with increase in chain length of the n-alcohol. The deviations u(D) of th e speeds of sound from the values calculated for ideal mixtures have been o btained from all measured values of mole fraction x. The behaviour of K-S,m (E) and u(D) with composition and the number of carbon atoms in the alcohol molecule is discussed. Also, the theoretical values of molar isentropic co mpressibility K-S,K-m and of speed of sound u have been calculated using th e Prigogine-Flory-Patterson (PFP) theory with the van der Waals (vdW) poten tial energy model and the results have been compared with experimental valu es.