Thermodynamic Properties of Solutions of m-Terphenyl in Benzene. I. The Vapor Pressures and the Related Thermodynamic Functions at 30 and 50°C

Abstract

Abstract Vapor pressures of solutions of m-terphenyl in benzene were measured for the concentration less than 0.23 in mole fraction x of terphenyl at 30 and 50°C. Vapor pressures P mmHg obtained are represented by log10P(30°)=2.076970–0.4343x–0.06569x2–0.4340x3 and log10P(50°)=2.432100–0.4343x–0.14654x2–0.3412x3. Chemical potentials observed were reproduced by the quasi-lattice theory for mixtures of molecules of different sizes. The Miller-Guggenheim expression (r=3, z=6–8) gives w⁄k=100±5°, and the Flory-Huggins expression (r=molecular volume ratio) gives χ=0.272±0.004 (30°) and χ=0.243±0.006(50°). Partial molar heats of mixing are rather fitted by the regular solution theory similarly to the case for benzene+biphenyl, and the Flory-Huggins expression gives a concentration-dependent enthalpy parameter, χH=(0.772+1.716φ)×102⁄T, where φ means a volume fraction of terphenyl. The average value of χH, 0.39 agreed with a theoretical estimate from solubility parameters.