Vapor equilibrium

The liquid -vapor equilibria, along the vaporization curve is expressed as ... 

Liquid-Vapor Equilibria using the Wang-Landau Algorithm... 

Kretschmer, C.B., Nowakowska, J., Wiebe, R. (1948) Densities and liquid-vapor equilibria of the system ethanol-isooctane (2,2,4-trimethylpentane) between 0 and 50°. J. Am. Chem. Soc. 70, 1785-1790. 

Note 1 An alternative definition of critical solution point refers strictly to liquid-vapor equilibria [3]. 

One can also consider the liquid/vapor equilibria in a simple (c = 1) two-phase system with /Xvap 7 liq. 

Several formal and informal intercomparisons of nitric acid measurement techniques have been carried out (43-46) these intercomparisons involve a multitude of techniques. The in situ measurement of this species has proven difficult because it very rapidly absorbs on any inlet surfaces and because it is involved in reversible solid-vapor equilibria with aerosol nitrate species. These equilibria can be disturbed by the sampling process these disturbances lead to negative or positive errors in the determination of the ambient vapor-phase concentration. The intercomparisons found differences of the order of a factor of 2 generally, and up to at least a factor of 5 at levels below 0.2 ppbv. These studies clearly indicate that the intercompared techniques do not allow the unequivocal determination of nitric acid in the atmosphere. A laser-photolysis, fragment-fluorescence method (47) and an active chemical ionization, mass spectrometric technique (48) were recently reported for this species. These approaches may provide more definite specificity for HN03. Challenges clearly remain in the measurement of this species. 

In all the above discussions regarding liquid-vapor equilibria we have assumed that our representative systems were ideal, that is, there are no differences in attractions between molecules of different types. Few systems are ideal and most show some deviation from ideality and do not follow Raoult s law. Deviations from Raoult s law may be positive or negative. Positive deviations (for binary mixtures) occur when the attraction of like molecules, A-A or B-B, are stronger than unlike molecules, A-B (total pressure greater than that computed for ideality). Negative deviations result from the opposite effects (total pressure lower than that computed for ideality). A mixture of two liquids can exhibit nonideal behavior by forming an azeotropic mixture (a constant boiling mixture). 

The characteristics of the primary surfaces and the derived surface for the solid-liquid equilibria and the solid-vapor equilibria are identical to those for the liquid-vapor equilibria with the exception that no critical phenomena have ever been observed in these two equilibria. Thus, a plane, tangent to the solid and liquid surfaces, may be rolled along these surfaces. The projections of the loci of the points of tangency are represented by the lines al and bs in Figure 5.5. If the points of tangency are connected by a straight line lying in the plane at any position of the plane, a ruled surface is derived... 

The thermodynamic treatment of data obtained from the study of the liquid-vapor equilibria at constant pressure differs from that used in constant-temperature experiments in the treatment of the standard states. This difference arises because we cannot calculate the change in the chemical... 

Water Ice/Liquid Water/Water Vapor Equilibria... 

Treybal, R.E., Weber, L.D., Daley, J.F. (1946) The system, acetone-water-1,1,2-trichloroethane. Ternary liquid and binary vapor equilibria. Ind. Eng. Chem. 38, 817-821. 

If we were to utilize Maxwell s equal-area construction, since the H-h plot in Figure 1.15(d) resembles a van der Waals isotherm in liquid-vapor equilibria [93], then Figures 1.15(c) and 1.15(d) would be qualitatively similar. Related issues can be further investigated via a stability analysis as described in Section II.D. 

In recent years, studies of the phase behavior of salt-water systems have primarily been carried out by Russian investigators (headed by Prof. Vladimir Valyashko) at the Kurnakov Institute in Moscow, particularly for fundamental understanding of the phase behavior of such systems. Valyashko [37,39,42,43], Ravich [38], Urosova and Valyashko [40], and Ravich et al. [41] have given a classification of the existence of two types of salts, depending on whether the critical behavior is observed in saturated solutions. Type 1 does not exhibit critical behavior in saturated solutions. The classic example of Type 1 is the NaCl-water system and has been studied by many authors [36,37,44-47]. The Type 2 systems exhibit critical behaviors in saturated solutions, and therefore have discontinuous solid-liquid-vapor equilibria. Table 1 shows the classification of binary mixtures of salt-water systems. 

Therefore, we designed and built a new apparatus, capable of investigating liquid-liquid-vapor equilibria (LLVE) and solid-liquid-vapor equilibria (SLVE) of complex systems with non-volatile components such as drugs or polymers. 

Several alternative versions may be found for dealing with liquid-vapor equilibria Beginning with the relation... 

Davalos, J., W.R. Anderson, R.E. Phelps, and A.J. Kidnay. 1976. "Liquid-Vapor Equilibria at 250.00 K for Systems Containing Methane, Ethane, and Carbon Dioxide", /. Chem. Eng. Data, 21 81-84. 

If carbon monoxide is initially present (case of synthesis gases produced by partial oxidation or steam reforming, for example), a residua] content is inevitable in the purified gas. This can at best be reduced to XS per cent volume, a maximum purity corresponding to the value given by the liquid/vapor equilibria of the H2/CO mixture at the service pressure(3to4.10 Paabsolute),aj atthemaximumcoolingtemperature(S — 155 0. A methane carbon monoxide column can finally be used to separate the CO. 

As discussed in Sec. 4, the K value of a species is a complex function of temperature, pressure, and equilibrium vapor- and hquid-phase compositions. However, for mixtures of compounds of similar molecular structure and size, the K value depends mainly on temperature and pressure. For example, several major graphical K-value correlations are available for light-hydrocarbon systems. The easiest to use are the DePriester charts [Chem. Eng. Prog. Symp. Ser. 7, 49, 1 (1953)], which cover 12 hydrocarbons (methane, ethylene, ethane, propylene, propane, isobutane, isobutylene, n-butane, isopentane, n-pentane, n-hexane, and n-heptane). These charts are a simplification of the Kellogg charts [Liquid-Vapor Equilibria in Mixtures of Light Hydrocarbons, MWK Equilibrium Constants, Polyco Data, (1950)] and include additional experimental data. The Kellogg charts, and hence the DePriester charts, are based primarily on the Benedict-Webb-Rubin equation of state [Chem. Eng. Prog., 47,419 (1951) 47, 449 (1951)], which can represent both the liquid and the vapor phases and can predict K values quite accurately when the equation constants are available for the components in question. 

The selected value is an average based on the equilibrium data summarized below. Drowart and co-workers have used the Knudsen effusion-mass spectrometric technique to determine the vapor equilibria over the systems SiC-graphite ( ), SiC-silison (2 ) and boron-carbon-silicon (3). 3rd law analysis of the partial pressures of C Si and Si lead to the concordant values -1 ... 

Carey, J. S. and Lewis, W. K. (1932) Ind Eng Chem. 24, 882. Studies in distillation. Liquid-vapor equilibria of ethyl alcohol-water mixtures. 

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