Thermodynamic Properties of Furan

A sample of furan was purified and used for calorimetric studies and for measurement of vapor pressure, density, refractive index, infrared spectrum (2 to 15..mu..) and mass spectrum. The heat of formation of liquid furan (-..delta..H/sub t/ = 14.90 kcal mole/sup -1/) was derived from heat of combustion measurements. Low temperature thermal studies included measurement of the heat capacity of the solid, transition temperature (150.0/sup 0/K), heat of transition (489.2 cal. mole/sup -1/), triple point (187.55/sup 0/K), heat of fusion (908.8 cal. mole/sup -1/) and heat capacity of the liquid. The entropy of the liquid at 298.16/sup 0/K, calculated from these data is 42.22 cal. deg./sup -1/ mole/sup -1/. The observed vapor pressures between 2 and 62/sup 0/ are represented by the equation log/sub 10/p (mm) = 6.97523 - 1060.851 (t + 227.740). The heat of vaporization at the normal boiling point (31.36/sup 0/) is 6474 cal. mole/sup -1/. The vapor heat capacity, measured at five temperatures between 317 and 488/sup 0/K, is given by the equation C/sup 0/psub p/ = -7.55 + 9.352 x 9.352 x 10/sup -2/T - 5.287 x 10/sup -6/ T/sup 2/ cal. deg./sup -1/ mole/sup -1/. The equation B = -279 - 22.6 exp(950/T) cc mole/sup -1/ was derived for the second virial coefficient from calorimetric data. A vibrational assignment which was partly empirical was made and used with molecular structure data to compute thermodynamic functions of the ideal gas to 1500/sup 0/K. The heat, free energy and equilibrium constant of formation at temperatures to 1500/sup 0/ were calculated using appropriate calorimetric data and thermodynamic functions.