Immiscibility diagrams

Fig. 3.10c in that a solution must be achieved by trial and error. If, however, the solvent and carrier are completely immiscible, diagrams may be conveniently used. 

Determination of immiscibility diagrams usually involves a large number of experimental measurements. The locus of the immiscibility boundary is often determined by heat treating a series of samples of constant bulk composition at different temperatures, quenching these samples, and determining if the sample is phase separated by visual observation of opalescence. The temperature of immiscibility is defined as the temperature bracketed by samples which either are or are not opalescent. The accuracy with which this temperature can be defined is determined by the temperature interval between treatments, and thus depends on the number of samples used. This process must be repeated for other compositions until the complete immiscibility boundary is well defined. 

APPLICATION OF IMMISCIBILITY DIAGRAMS 6.1 Binary Immiscibility Diagrams... 

Figrue 4.8 Metastable immiscibility diagram for the sodium silicate system... 

The spinodal boundary is rarely shown on ternary immiscibility diagrams. Since this boundary is also represented by a dome, similar contour lines could be drawn. However, since the spinodal boundary is rarely known for these systems, it is usually neglected in the presentation of ternary immiscibility regions. 

Consider the sodium silicate immiscibility diagram shown in Figure 4.8. Describe the morphology for samples equilibrated at 700 °C which contain (a) 4 mol% soda, (b) 10 mol% soda, or (c) 15 mol% soda. Determine the compositions of the two phases which co-exist in each sample. Determine the relative amounts of each phase for each sample. 

Liquid—Hquid equiHbria having more than three components caimot as a rule be represented on a two-dimensional diagram. Such systems are important in fractional extraction, for example, operations in which two consolute components C and D are separated by means of two solvents A and B. For the special case where A and B are immiscible, the linear distribution law can be appHed to components C and D independendy ... 

Fig. 5. Flow diagram of typical interfacial polymerisation encapsulation process in which reactants X and Y are dissolved in separate mutually immiscible...

Ternary-phase equilibrium data can be tabulated as in Table 15-1 and then worked into an electronic spreadsheet as in Table 15-2 to be presented as a right-triangular diagram as shown in Fig. 15-7. The weight-fraction solute is on the horizontal axis and the weight-fraciion extraciion-solvent is on the veriical axis. The tie-lines connect the points that are in equilibrium. For low-solute concentrations the horizontal scale can be expanded. The water-acetic acid-methylisobutylketone ternary is a Type I system where only one of the binary pairs, water-MIBK, is immiscible. In a Type II system two of the binary pairs are immiscible, i.e. the solute is not totally miscible in one of the liquids. 

The basis for the separation is that when two polymers, or a polymer and certain salts, are mixed together in water, they are incompatible, leading to the formation of two immiscible but predominantly aqueous phases, each rich in only one of the two components [Albertsson, op. cit. Kula, in Cooney and Humphrey (eds.), op. cit., pp. 451 71]. A phase diagram for a polyethylene glycol (PEG)-Dextran, two-phase system is shown in Fig. 22-85. Proteins are known to distribute unevenly between these phases. This uneven distribution can be used for the selective concentration and partial purification of the products. Partitioning between the two phases is controlled by the polymer molecular weight and concentration, protein net charge and... 

Most pairs of homopolymers are mutually immiscible, so that phase diagrams are little used in polymer science... another major difference between polymers on the one hand, and metals and ceramics on the other. Two-phase fields can be at lower or higher temperatures than single-phase fields... another unique feature. 

Case I. At sufficiently low pressures, the solubility curve does not intersect the coexistence curve. In this case, the gas solubility is too low for liquid-liquid immiscibility, since the coexistence curve describes only liquid-phase behavior. Stated in another way, the points on the coexistence curve are not allowed because the fugacity f2L on this curve exceeds the prescribed vapor-phase value f2v. The ternary phase diagram therefore consists of only the solubility curve, as shown in Fig. 28a where V stands for vapor phase. 

Case II. ai3 > oti2- In this case, the tie lines slope toward the 1-3 binary line. This could have been intuitively predicted by considering the limiting case of an immiscibility band across the phase diagram, as shown in Fig. 31C. Of necessity, the tie lines become parallel to either the 1-3 or the 2-3 binary lines in the limit of pure 1-3 binary or pure 2-3 binary, respectively. 

On an atomic basis, Li is much more soluble in K than vice versa (0.07, 0.43, 1.29 and 1.99 mol% Li compared with 0.007, 0.02, 0.05 and 0.07 mol% K). Although these solubilities are larger than those given by eqs. (a) and (b), both investigations point to a two-immiscible-liquid-type of phase diagram with a consolute T > 1000°C, and with the consolute composition being on the Li-rich side as in the Li-Na system. 

V. Gobry, F. Re5miond and H. H. Girault, Refinment of Ionic Partition Diagrams and Determination of Partition Coefficients of Multiprotic Compounds by Electrochemistry at the Interface between Two Immiscible Electrolyte Solutions, submitted. 

Fig. 1. Schematic diagram illustrating the analogies between dispersion of immiscible liquids and dispersed solids.

When a reversible transition from one monolayer phase to another can be observed in the 11/A isotherm (usually evidenced by a sharp discontinuity or plateau in the phase diagram), a two-dimensional version of the Gibbs phase rule (Gibbs, 1948) may be applied. The transition pressure for a phase change in one or both of the film components can be monitored as a function of film composition, with an ideally miscible system following the relation (12). A completely immiscible system will not follow this ideal law, but will... 

Fig. 11 Defay-Crisp diagram for a binary monolayer A, ideal mixing B, non-ideal mixing C, complete immiscibility. and n2 are the phase transition pressures of components 1 and 2.

Figure 5.2. Miscibility diagram (and solubility gaps) of water and organic-phase liquids. Solvents not connected by a binding line in Figure 5.2 are immiscible solvents of unlimited miscibility are connected by a solid line, those of limited miscibility by a dotted line [16]...

Figure 5.9 Phase diagram showing liquid immiscibility in the Na2BgOi3-Si02 system below the liquidus [16].

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