SOLUBILITIES OF NITROGEN IN MIXED SOLVENTS: CYCLOHEXANE-iso-OCTANE AND n-PROPANOL-iso-OCTANE MIXTURES

Solubility measurements of nitrogen in two mixed solvents, cyclohexane-iso-octane [1] and n-propanol-iso-octane [2], were performed at 25°C and atmospheric pressure. The experimental "excess quantity" over Henry''s constant averaged in the volume fraction of solvent (lnκ) is slightly positive for both systems. Based upon the solution theory of Flory-Huggins type, the excess quantity lnκ is described by the following three terms; (a) size term based upon the difference of solvent molar volumes (positive), (b) physical interaction term (negative), and (c) association term (negative). For system [1] the association term is zero. Each term is calculated from the characteristic properties of the binary liquid mixture and the molar volume of solute gas, and agreement between the calculated and experimental values for lnκ is very satisfactory. Contribution of term (a) to the excess quantity κ is the largest for the systems investigated. For the solubility of nitrogen in mixture [2] the contribution of the association term (c) to r is smaller than that of term (b), whereas the association term contributes more than 90% in the excess Gibbs energy for the binary mixture [2].