Phase equilibria quaternary

An example for a partially known ternary phase diagram is the sodium octane 1 -sulfonate/ 1-decanol/water system [61]. Figure 34 shows the isotropic areas L, and L2 for the water-rich surfactant phase with solubilized alcohol and for the solvent-rich surfactant phase with solubilized water, respectively. Furthermore, the lamellar neat phase D and the anisotropic hexagonal middle phase E are indicated (for systematics, cf. Ref. 62). For the quaternary sodium octane 1-sulfonate (A)/l-butanol (B)/n-tetradecane (0)/water (W) system, the tricritical point which characterizes the transition of three coexisting phases into one liquid phase is at 40.1°C A, 0.042 (mass parts) B, 0.958 (A + B = 56 wt %) O, 0.54 W, 0.46 [63]. For both the binary phase equilibrium dodecane... 

A general formulation of the problem of solid-liquid phase equilibrium in quaternary systems was presented and required the evaluation of two thermodynamic quantities, By and Ty. Four methods for calculating Gy from experimental data were suggested. With these methods, reliable values of Gy for most compound semiconductors could be determined. The term Ty involves the deviation of the liquid solution from ideal behavior relative to that in the solid. This term is less important than the individual activity coefficients because of a partial cancellation of the composition and temperature dependence of the individual activity coefficients. The thermodynamic data base available for liquid mixtures is far more extensive than that for solid solutions. Future work aimed at measurement of solid-mixture properties would be helpful in identifying miscibility limits and their relation to LPE as a problem of constrained equilibrium. 

Phase Equilibrium of the Quaternary System Furfural-Acetic Acid-Water-CC>2... 

The phase behavior observed in the quaternary systems A and B is also evidenced in ternary systems. Figure 4 shows the phase diagrams for systems made of AOT-water and two different oils. The phase diagram with decane was established by Assih (14) and that with isooctane has been established in our laboratory. At 25°C the isooctane system does not present a critical point and the inverse micellar phase is bounded by a two-phase domain where the inverse micellar phase is in equilibrium with a liquid crystalline phase, as for system B or system A when the W/S ratio is below 1.1. In the case of decane, a critical point has been evidenced by light scattering (15). Assih and al. have observed around the critical point a two-phase region where two microemulsions are in equilibrium. A three-phase equilibrium connects the liquid crystalline phase and this last region. 

Solution. Experimental phase equilibrium data for the quaternary system were fitted to the NRTL equation by Cohen and Renon. The resulting binary pair constants in (5-68) and (5-69) are... 

In principle, it would be desirable to have information on vapor-liquid equilibria of all binary systems in the temperature range in which the RD is carried out, which is about 100-150 °C in the case studied here. Furthermore, it would be desirable to have at least some data points for ternary systems (all of which are reactive) and for the quaternary system to be able to check the predictive power of the phase equilibrium model. That ideal situation is almost never encountered in reality. In many cases, even reliable experimental data on the binary systems is missing. In the present study, no data was available for the binary systems acetic acid + hexyl acetate and 1-hexanol - - hexyl acetate. Estimations of missing data using group contribution methods such as UNIFAC are possible, but their quality is often hard to assess. 

The prerequisite of all types of extraction processes is the existence of a large miscibility gap between raffinate and extract. The thermodynamic principles of phase equilibrium are dealt with in Chap. 2. An extensive collection of liquid-liquid equilibria is given in the Dechema Data Collection (Sorensen and Arlt 1980ff). Volume 1 contains data of miscibility gaps of binary systems. Phase equilibrium data (miscibility gaps and distribution equilibrium) of ternary and quaternary mixtures are listed in volumes 2-7. 

Kordikowski, A. and Schneider, G.M. (1995) Fluid phase equilibrium studies on ternary and quaternary mixtures of carbon dioxide with 1-dodecanol, dodecanoic acid, quinoxahne and 1,8-octanediol at 393.2 K and at pressures up to 40 MPa, Fluid Phase Equilibria 105, 129-139. 

Stable phase equilibrium of the quaternary system (NaCI - KCl - Na2B407 - K2B4O7 - H2O) at 298.15 K... 

The stable phase equilibrium experimental results of solubilities of the quaternary system (NaCl - KCl - Na2B407 - K2B4O7 - H2O) at 298.15 K were determined, and are listed in Table 3, respectively. On the basis of the Janecke index (/b, /b/ [mol/100 mol(2Na+ + 2K+)]) in Table 3, the stable equilibrium phase diagram of the system at 298.15 K was plotted and shown in Figure 5. 

A comparison of the dry-salt diagrams of the metastable phase equilibrium at 308.15 K and the stable phase equilibrium at 298.15 K for the same system is shown in Figure 8. The metastable crystallization regions of borax and potassium chloride are both enlarged while the crystallized area of other minerals existed is decreased. When compared with the stable system, the solubility of borax in water in the metastable system is increased from 3.13 % to 5.70 %. The metastable phenomenon of borax is obvious in this reciprocal quaternary system. 

In order to illustrate the phase behaviour of microemulsions, it is most convenient to consider the systems with nonionic surfactants of the ethylene oxide type. These have been studied extensively by Shinoda and Kunieda and co-workers and by Kahlweit and Strey and co-workers (for more recent reviews, see, e.g. refs (9) and (10)). At low surfactant concentrations, there is a general sequence of phase equilibria, often referred to as Winsor equilibria (11). The equilibrium conditions for the microemulsion phase, L, changes from equilibrium with excess oil (Winsor I) to equilibrium with excess water (Winsor II), via a three-phase equilibrium with excess water and oil (Winsor III). For nonionics, this sequence occurs when increasing the temperature, while for quaternary or ternary systems, it can be observed with increasing salinity or cosurfactant-to-surfactant ratio. 

Gordon JE (1965) Fused organic salts. IV. Characterization of low-melting quaternary ammonium salts. Phase equilibrium for salt-salt and salt-nonelectrolyte systems. Proptuties of the liquid salt medium. J Am Chem Soc 87 4347-4358... 

On the other hand, it can be said from a scientific viewpoint that data for fundamental parameters are lacking. For instance, the influence of additional elements on diffusivity and activity of relevant elements is poorly known. Phase equilibrium diagrams of tertiary and quaternary systems are very few. These are indispensable for theoretical understanding of the phase relations. The mechanism of the influence of combined addition of alloying elements is unclear, although the most suitable combination would be made from the viewpoints of production cost, environmental protection and high performance. 

Using UNIQUAC, Table 2 summarizes vapor-liquid equilibrium predictions for several representative ternary mixtures and one quaternary mixture. Agreement is good between calculated and experimental pressures (or temperatures) and vapor-phase compositions. ... 

In some cases, the Q ions have such a low solubility in water that virtually all remain in the organic phase. ° In such cases, the exchange of ions (equilibrium 3) takes place across the interface. Still another mechanism the interfacial mechanism) can operate where OH extracts a proton from an organic substrate. In this mechanism, the OH ions remain in the aqueous phase and the substrate in the organic phase the deprotonation takes place at the interface. Thermal stability of the quaternary ammonium salt is a problem, limiting the use of some catalysts. The trialkylacyl ammonium halide 95 is thermally stable, however, even at high reaction temperatures." The use of molten quaternary ammonium salts as ionic reaction media for substitution reactions has also been reported. " " ... 

All chemicals used were of very high purity grade (>99 %). The quaternary systems were mixed and allowed to reach equilibrium over a week at constant temperature, with occasional stirring. The oil phase (top phase) was placed in the measuring cell of the pendant drop apparatus. The bottom (aqueous) phase was filled in the syringe for the measurement. 

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