Molar Excess Volumes and Excess Isentropic Compressibilities of Ternary Mixtures Containing 2-Pyrrolidinone

Molar excess Volumes, Vijk and speeds of sound , uijk of 2-pyrrolidinone (i) + benzene or toluene (j) + ethanol (k) ternary mixture have been measured as a function of composition at 308.15 K. The observed speeds of sound data have been utilized to determine excess isentropic compressiblities, ( E S κ )ijk of ternary (i + j + k) mixtures. Molar excess volumes, Vijk and excess isentropic compressibilities, ( E S κ )ijk data have fitted to the Redlich-Kister equation to calculate ternary adjustable parameters and standard deviations. The Moelywn-Huggins concept (Huggins in Polymer 12: 389-399, 1971) of connectivity between the surfaces of the constituents of binary mixtures has been extended to ternary mixtures (using the concept of a connectivity parameter of third degree of molecules, ξ , which inturn depends on its topology) to obtain an expression that describes well the measured Vijk and ( E S κ )ijk data. Keywords—Connectivity parameter of third degree, ξ, Excess isentropic compressibilities,( E S κ )ijk, Interaction energy parameter, χ, Molar excess volumes, Vijk, Speeds of sound, uijk.