Immiscibility region

To form an immiscible region [Pg.203]

Figure 7.12 Successive snapshots of a binary A/B system in the immiscible region of coexisting A-rich (lighter) and B-rich (darker) liquid phases (Fig. 7.11), comparing the T-dependent behavior for noncritical (upper sequence cf. dashed line in Fig. 7.11) versus critical composition (lower sequence cf. dotted line in Fig. 7.11), and showing how the meniscus rises out of the container in the first case but vanishes at the critical point Tc in the second case. [Both solutions are taken to be fairly comparable in the starting low-71 snapshot, but their deviations are readily apparent in the second snapshot at the temperature Ttie of the horizontal tie-line in Fig. 7.11.]...

Nisoli et al. [22] have studied the attainable regions for this reaction system with simultaneous distillative separation. These authors found an immiscible region between water and DME, which shrinks as the pressure increases. The PSPS of this system was calculated based on the VLE parameters given in the studies of Nisoli et al. [22]. Water was chosen as the reference component and DME as independent variable to represent the system ... 

FIGURE 11-21 Schematic phase diagram showing the single phase (miscible) and phase-separated (immiscible) regions. 

FIG. 20. Solid solutions of feldspars the hatched area represents the immiscibility region. 

A similar plot of 8(B03) for the series of ternary sodium borosilicate glasses shows a similar trend with the mole fraction of Si02 (x) but with much greater scatter even when the compositions in the immiscibility region are omitted (Martens and Miiller-Warmuth 2000) (Figure 7.14B). The fitted line to these data is given by ... 

In this process phase inversion is introduced by lowering the temperature of the polymer solution. A polymer is mixed with a substance that acts as a solvent at a high temperature and the polymer solution is cast into a film. When the solution is cooled, it enters into an immiscible region due to the loss of solvent power. Liquid-liquid demixing occurs and the solution is separated into two phases, i.e., the polymer-lean phase is dispersed as droplets in the polymer-rich phase. Further, cooling causes gelation of polymer. Because the solvent is usually nonvolatile, it must be removed with a liquid that is miscible with the solvent but not miscible with the polymer. The membranes made by the TIPS method have pore sizes in the range of 0.1 and 1 pm and the pore structure is uniform in the depth direction. ... 

The immiscibility region near the Si02 apex was neglected in the calculation as such behavior is not considered in the thermodynamic model. Furthermore, because of the lack of thermodynamic data, the crystallization of rankinite, tricalcium silicate, tricalcium aluminate, and calcium hexaaluminate was not included in the calculation. 

The liquids in the immiscible region boil at a constant temperature of about... 

A schematic representation of type-I ternary phase behavior is shown in figure 3.29. The three diagrams in this figure represent mixtures at a fixed temperature slightly higher than the critical temperature of the SCF but at three different pressures. The distinguishing feature of type-I ternary phase behavior is the absence of LLV immiscibility regions within the ternary... 

The first term describes the contribution of the ideal mixing itself, while the second one describes the excess energy due to interactions The variation can exhibit a particular shape, as Illustrated by a numerical example in the Figure 6.18, where the activity coefficients have been calculated by Margules model with A,2=2 and A2,=1.5. It may be observed that in the immiscibility region a-b the value, resulting by... 

The binary mixture water (1) / butanone (2) exhibits an interesting phase behaviour the azeotrope lies outside the immiscibility region. Study the ability of a liquid activity model to describe accurately both VLE and LLE. 

Solution. We present results of regression obtained in ASPEN Plus with NRTL model. Experimental data comes from Landolt-Bomstein. Fig. 6.21 displays the comparison of data at 1.033 at when both VLE and LLE data have been combined. The accuracy is excellent. Both immiscible region and position of the azeotrope are correctly described. Fig. 6.22 displays at the split temperature of 73.2 C. The characteristic concave shape is reproduced. As before, the variation is sharper at the water-rich zone limit. 

The effect of the variation of the molecular mass of the polymer on the equilibrium lines is comparable to the effect of gas concentration. This is due to the fact that small solvent molecules dissolve small molecules better than bigger ones. Thus, by increasing the molecular weight of the polymer, the immiscibility region is expanded. UCST and LCST move toward each other until they eventually merge to the hour glass shape. The effect of several variables on the location of the UCST and LCST is qualitatively illustrated in Figure 15.4. 

To explain the behavior of a polymeric multicomponent system, the polymer is considered as a mixture of two polymer species, PI and P2. By doing this, the polymer-solvent system can be illustrated using a ternary Gibbs triangular diagram. It is assumed that one species of the polymer, PI, has a lower molecular mass than P2 and is completely miscible with the solvent, whereas P2 exhibits an immiscibility region (Figure 15.5). 

Adding solvent to a polymer mixture F at T, the immiscibility region is entered at point Cl, where the solution turns cloudy. This is why this point is also called cloud point. At this moment, a second phase appears whose concentration is given by SI. Since the amount of the second phase is so small, its concentration is experimentally not accessible and this point is named shadow point. Adding more solvent, the two-phase region is finally left at the other side at the cloud point C2 with the corresponding shadow point S2. 

At Other temperatures, the shape of the immiscibility region differs. For example, at a higher temperature T2, it could be that the two-phase region is entered at its critical point, and so both phases have the same concentration. However, they can still be distinguished by their different densities. Or, at an even higher temperature Fj, the two-phase region is tangented at only one point. This would be the UCST. 

Figrue 4.2 Idealized immiscibility region in a binary system... 

Reheating of glasses to temperatures above Tg and within the immiscibility region can often alter their micro structures. If we consider a sodium silicate glass containing 15 mol% soda formed by rapid... 

---