Vapor-liquid equilibrium infinite dilution values

The values of the activity coefficients here are very large, especially compared with those we found previously from vapor-liquid equilibrium data. Such values for the activity coefficient of the dilute species in a mixture with species of very different chemical nature, such as carbon tetrachloride and water, is quite common. Note that because of the concentrations involved, the activity coefficients found are essentially the values at infinite dilution. ... 

Henry s lxm> Constant Henry s law for dilute concentrations of contaminants in water is often appropriate for modeling vapor—liquid equilibrium (VLE) behavior (47). At very low concentrations, a chemical s Henry s constant is equal to the product of its activity coefficient and vapor pressure (3,10,48). Activity coefficient models can provide estimated values of infinite dilution activity coefficients for calculating Henry s constants as a function of... 

From the isothermal vapor-liquid equilibrium data for the ethanol(l)/toluene(2) system given in Table 1.11, calculate (a) vapor composition, assuming that the liquid phase and the vapor phase obey Raoult s and Dalton s laws, respectively, (b) the values of the infinite-dilution activity coefficients, Y and y2°°, (c) Van Laar parameters using data at the azeotropic point as well as from the infinite-dilution activity coefficients, and (d) Wilson parameters using data at the azeotropic point as well as from the infinite-dilution activity coefficients. 

So that an azeotrope with acetone does not form, the alcohol used must have a high enough boiling point. This requirement is reliably established only if vapor-liquid equilibrium data for at least two, preferably three, of the members of the series with acetone are known. The Pierotti-Deal-Derr method (4) (discussed later) or the Tassios-Van Winkle method (5) can be used in this case. In the latter method a log-log plot of y°i vs. P°i should yield a straight line. Figure 1 presents results for n-alco-hols and benzene from the isobaric (760 mm Hg) data of Wehe and Coates (6). Reliable infinite dilution activity coefficients are established for the other n-alcohols from data for at least two, and preferably three, of them. These y° values are used with equations like those of Van Laar or Wilson (7) to generate activity coefficients at intermediate compositions and to check for an existing azeotrope or a difficult separation (x-y curve close to the 45° line). 

NONIDEAL LIQUID MIXTURES 3.5 K VALUE FOR IDEAL LIQUID PHASE, NONIDEAL VAPOR PHASE 3.7 K VALUE FOR IDEAL VAPOR PHASE, NONIDEAL LIQUID PHASE 3.8 THERMODYNAMIC CONSISTENCY OF EXPERIMENTAL VAPOR-LIQUID EQUILIBRIUM DATA 3.8 ESTIMATING INFINITE-DILUTION ACTIVITY COEFFICIENTS 3.10... 

The quantity ffsv represents the surface energy associated with equilibrium between the solid surface and the vapor of the liquid (wet systems). If vacuum conditions prevail (dry systems), the surface energy of the solid/vacuum interface is represented by the term infinitely dilute vapor. A solid surface in the presence of vapor differs from a solid surface in vacuum by the degree of adsorption of vapor molecules on the solid surface—a process that can occur spontaneously and thus can result in a lower surface... 

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