Effect of Molecular Structure on the Thermodynamics of Nitromethane+Butanol Isomers Near the Upper Critical Point

Densities, isentropic compressibilities, and isobaric molar heat capacities were determined over the whole composition range for nitromethane+(2-butanol or isobutanol) at atmospheric pressure and at the temperatures 288.15, 293.15, 298.15, and 308.15 K. These results allowed us to obtain isobaric thermal expan- sivities, isothermal compressibilities, and isochoric molar heat capacities at the temperature 298.15 K. The excess quantities for the given properties were obtained. In addition, liquid liquid phase separation temperatures were also determined, locating upper critical solution temperatures near the experimental temperatures. The variation of the properties among isomers is discussed. Also, the effect of the nonrandomness of the mixtures expected near the critical point is discussed.