Second virial coefficient of ethanol from measurements of the excess molar enthalpy of ethanol–nitrogen

Abstract

Flow calorimetric measurements of the excess molar enthalpy H^E_m of [xC₂H₅OH–(1–x)N₂](g) are reported. The measurements extend over the range 333.9–412.5 K at pressures from 32.7 to 95.1 kPa. These are analysed in terms of an association model involving dimer, trimer and tetramer equilibria. Dispersion and dipolar forces were estimated by using flouroethane as a homomorph for ethanol. Cross-term virial coefficients were small, and could be adequately estimated on this basis. As preliminary calculations showed that the measurements could be fitted by assuming only dimer and tetramer equilibria, this model was adopted. The dimer + tetramer model was found to fit literature values of the isobaric heat capacity and isothermal Joule–Thomson coefficients measured at several temperatures and pressures. Second virial coefficients have been derived from the analysis and a simple equation for B(T) is given.