The Vapor-Liquid and Liquid-Liquid Phase Equilibria for the Partially Miscible System Methanol-Cyclohexane

By use of techniques of previous workers for determining liquid-liquid equilibrium and through the use of a circulation still, the complete phase diagram for the partially miscible system, methanol-cyclohexane, was determined. Tile accuracy of earlier liquid-liquid phase data was not improved upon although it was closely approximated. The critical solution temperature was found to be 46.4 degrees C., which is within the range of temperatures reported in earlier measurements. Activity coefficients of methanol and cyclohexane were calculated from the phase boundaries of the boiling point diagram determined in the present investigation. These activity coefficients were in agreement with the Gibbs-Duhem equation and with the theoretically predicted activity coefficients of the van Laar and Margules equations. Vapor-liquid phase data previously available was limited to the azeotrope boiling temperature reported to be 54.2 degrees C