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The phase behavior and solubility relations of the benzene‐water system

1959; Wiley; Volume: 5; Issue: 3 Linguagem: Inglês

10.1002/aic.690050307

1547-5905

Charles J. Rebert, Webster B. Kay,

Surfactants and Colloidal Systems

Abstract In order to contribute to knowledge of the nature of the phase behavior of partially miscible liquid systems, a study of the benzene‐water system was undertaken. The pressures at liquid‐ and vapor‐phase boundaries of fifteen mixtures of benzene and water were determined within the temperature range of 200 to 357°C. Along with a complete numerical tabulation, these data are presented graphically as pressure‐temperature, pressure‐composition, and temperature‐composition phase diagrams to show the nature of the boundaries. Up to the three‐phase critical end point, the benzene‐water system develops in a manner usually ascribed to a partially miscible system in which the vapor compositin at a point of univariance lies intermediate to the two liquid compositions. The three‐phase critical end point occurs at 1,364 1b./sq. in. abs. and 268.3°C., and the composition of the critical phase is 25.8 weight % water, with the remaining liquid phase 92.8 weight % water. The pressure, temperature, and composition of the critical solution end point are deduced as 2,300 1b./sq. in. abs., 306.4°C., and 59 weight % water, respectively. At temperatures between these two critical points the phase behavior is likened to that of a dense gas or fluid dissolved in a liquid. Definite limiting values of temperature and pressure are assignable to this behavior by the extension of the three‐phase curve up to the critical solution end point. This extended curve is not a phase boundary, but the temperature and pressure at a given point on the curve represents in a mixture of fixed composition the limit of mutual solubility of the benzene‐rich fluid phase and the water‐rich phase. At a temperature above or a pressure below the given point the liquid phase begins to vaporize. Above the critical solution end point the vapor‐liquid phase boundaries are like those of a normal binary mixture.