Liquid Equilibria in Binary Systems

In the previous sections we have been concerned with high-pressure equilibria in systems containing one liquid phase and one vapor phase. We now briefly consider the effect of pressure on equilibria between two liquid phases. In particular, we are concerned with the question of how pressure may be used to induce miscibility or immiscibility in a binary liquid system. 

Two liquids are miscible in all proportions if Ag, the molar Gibbs energy of mixing at constant temperature and pressure, satisfies the relations 

Since Ag is a function of pressure, it follows that, under certain conditions, a change in pressure may produce immiscibility in a completely miscible system, or, conversely, such a change may produce complete miscibility in a partially immiscible system. The effect of pressure on miscibility in binary liquid mixtures is closely connected with the volume change on mixing, as indicated by the exact relation 

To illustrate, let us consider a simple, symmetric binary mixture at some fixed temperature and 1-atm pressure. For this liquid mixture, let us assume that 

Equation (91) tells us that if AJRT 2 (complete miscibility at I atm) and if B 0, then there is a certain pressure P (larger than 1 atm) at which immiscibility is induced. On the other hand, if A/RT 2 (incomplete immisd-bility at 1 atm) and if B 0, then there is a certain pressure P (larger than 1 atm) at which complete miscibility is attained. 

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L termination, 62-63 Lewis fugacity rule, 144-145 Liquid-liquid equilibria in binary systems, 184-190 in ternary systems, 194-203 phase diagram, 196-202... 

Hamam, S.E.M. and Lu, B.C.-Y. 1976. Isothermal Vapor-Liquid Equilibria in Binary System Propane-Carbon Dioxide", /. Chem. Eng. Data, 21 200-204. 

Figure 1 Gas-liquid equilibria in binary systems schematic representation for symbols see Section 1). a, Three-dimensional representation in the p-T-x space , b, p T) projections of the phase diagrams...

Figure 12 Interference of solid-liquid and liquid-liquid equilibria in binary systems schematic representation see text = triple point temperature IAS Tq — quadruple point temperature LLSS)...

Gmehling, J, Isothermal vapor-liquid equilibria in binary systems formed by esters with alkenes J. Chem. Eng. Data 1983,28, 27-30... 

Gierycz, P. Rogalsid, M. Malanowski, S. Vapour-liquid equilibria in binary systems formed by N-methylpyrrolidone with hydrocarbons and hydroxyl derivatives Fluid Phase Equilib. 1985,22, 107-122... 

Alpert, N. and Elving, P. J. (1949). Vapor-liquid Equilibria in Binary Systems. Ethylene Dichloride-Toluene and Formic Acid Acetic Acid. T/id Eng. Chem. 41,2864-2869. 

Castellari, C. Francesconi, R. ComeUi, F. Vapor-liquid equilibria in binary systems containing 1,3-dioxolane at isobaric conditions. 3. Binary mixtures of 1,3-dioxolane with o-, m-, and p-xylenes. J. Chem. Eng. Data 1982, 27, 156-158. 

Ogorodnikov, S. K. Kogan, V. B. Nemtsov, M. S. Vapor-liquid equilibria in binary systems formed by hydrocarbons and acetone [Russ]. Zh. Prikl. Khim. (Leningrad) 1961, 34, 323-331. 

Galska-Krajewska, A. Vapor-liquid equilibria in binary systems, p-xylene - aliphatic alcohols under atmospheric pressure [Pol]. Rocz. Chem. 1967, 41, 609-616. 

Conner, A. Z. Elving, P. J. Steingiser, S. Vapor-liquid equilibria in binary system acetaldehyde dibutyl acetal - n-butanol. Ind. Eng. Chem. 1948, 40, 497-499. 

Fahmy, A. F. M. Assal, F. A. Vapour-liquid equilibria in binary systems of phenol and 2,4-lutidine with n-paraffins. Bull. Acad. Pol. Sci., Ser. Sci. Chim. 1966, 14, 661-666. 

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