Vapor-liquid composition curves

Binary copolymerization resembles distillation of a bicomponent liquid mixture, with a reactivity ratio corresponding to the ratio of vapor pressures of the pure components in the latter case. The vapor-liquid composition curves of ideal binary mixtures have no inflection points and neither do the polymer-composition curves for random copolymerizations, in which/ r2 — 1 (Fig. 7-1). For this reason, such comonomer systems are sometimes called ideal. 

The vapor-liquid composition curve for a normal mixture is given in Fig. 1-8. The lower curve is a plot of liquid composition against the boiling point of the mixture. The upper curve is a plot... 

Fig. 1-8. Vapor-liquid composition curve for a normal mixture.

Fig. 1 -9. Vapor-liquid composition curves for mixtures giving minimum and maximum boiling points.

Fig. 1-16. Vapor-liquid composition curve lor benzene-toluene mixtures.

Table 7.132 Vapor-LIquId Composition Curves for Aqueous Ethylene Glycol Solutions (23)... 

When an ideal solution of two liquids, such as benzene (bp 80°C) and toluene (bp 110°C), is distilled by simple distillation, the first vapor produced will be enriched in the lower-boiling component (benzene). However, when that initial vapor is condensed and analyzed, the distillate will not be pure benzene. The boiling-point difference of benzene and toluene (30°C) is too small to achieve a complete separation by simple distillation. Following the principles outlined in Technique 14, Section 14.2, and using the vapor-liquid composition curve given in Figure 15.1, you can see what would happen if you started with an equimolar mixture of benzene and toluene. 

The vapor-liquid composition curve for mixtures of benzene and toluene. 

Vapor - liquid composition curves for ethanol-water mixture a is the membrane selectivity for water over ethanol (8). 

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