Effect of cosolvents on solute separability between liquid phases in liquid–liquid–vapor ternary mixtures

The liquid–liquid–vapor (llg) partial miscibility behavior of the ternary mixtures carbon dioxide+1-methylnaphthalene+methanol was experimentally studied by use of a visual cell (stoichiometric) technique. Phase compositions and molar volumes of the two liquid phases in equilibrium are reported as functions of temperature and pressure within the llg region. In contrast to an earlier study using acetone as a cosolvent, the cosolvent methanol does not enhance the amount of the solute 1-methylnaphthalene taken up by the second (carbon dioxide-rich) liquid phase. Additional llg isotherms of the mixtures carbon dioxide+1-methylnaphthalene+n-hexane, and carbon dioxide+n-tetradecane+n-hexane were studied in order to elucidate the role that molecular similarity vis-à-vis dipole moment has on solute solubility enhancement in the second liquid phase l2.