Benzene-methanol association. The excess molar enthalpy and second virial cross coefficients of (benzene+methanol)(g) and (cyclohexane+methanol)(g)

New measurenaents of the excess molar enthalpy HI, , of (yCH3OH+ ( 1 - .v)C~, H~,)(g) and ( vCH~OH + ( I - ylC~,Hi,)(g)measured at standard atmospheric pressure over the temperature range 363.2 to 433.2 K are reported. These measuren~ents supplement earlier measurenaents made over the range 454.2 to 523.0 K at pressures up to 4.0 MPa. The nonideality of the methanol vapor is described using a quasi claemical model model in which only dimer and tetramer association equilibria are considered. The values of H~, for the (methanol +cyclohexanej(g) mixture were lbund to agree well with values calculated using the association model. For (methanol+benzene)(g) the experimental values of HI, ʹ were Ibund to be approximately 20% smaller than values calculated from the model and this was attributed to weak association between the unlike molecules. A quasi-chemical model used to describe the association between the unlike molecules yielded a wduc of the equilibrium constant Kt_,(298.15K)=0.22MPa i, and a wdue for the enthalpy of the methanol benzene association of AHL,= 13 kJ-mol i. Second virial crosscoefficients B~_, Ibr methanol cyclohexane and methanol-benzene have been derived from the HI~ ~ n-]easurements.