TEMPERATURE-DEPENDENCE OF EXCESS THERMODYNAMIC PROPERTIES OF ETHANOL + NORMAL-HEPTANE AND 2-PROPANOL + NORMAL-HEPTANE SOLUTIONS

Heat capacities of n-heptane, ethanol, 2-propanol, and their binary mixtures have been measured by adiabatic calorlmetry with an uncertainty of about 0.2%: n-heptane (184-302 K), ethanol (160-306 K), 2-propanol (188-304 K), five mixtures of ethanol + n-heptane (195-305 K), and five mixtures of 2-propanol + n-heptane (188-305 K). These data were used to obtain the excess heat capacity, CPE, for the solutions. The molar excess thermodynamic functions HE, GE, and SE were computed by using these CpE values, together with values of GE and HE at 303.15 K, reported by others. The variation of GEwith composition and temperature was correlated by using two forms of the Redlich-Kister equation, the Wilson equation, and the Wiehe-Bagley equation. The composition and temperature dependence of GE and HEof the above systems and the ethanol-methylcyclohexane system were used to test variations of the theory of associated solutions based on volume fraction and mole fraction statistics. © 1979, American Chemical Society. All rights reserved.