Phase diagram water-nicotine

Some substances exhibit both upper and lower consolute temperatures. The diagram for the system nicotine-water is shown schematically in Fig. 15.3(b). The lower consolute temperature is about 61 °C, the upper one about 210 °C. At all points in the closed loop two phases are present, while the points outside the loop represent homogeneous states of the system. 

Key characteristics in liquid/liquid systems are the mutual solubility and the concentration of both liquid phases in the equilibrium state. The previously discussed laws of mixed phase thermodynamics can still be applied. The feasibility of a liquid/liquid extraction depends on the occurrence of a miscibility gap and its width at different temperatures. Figure 2.2-1 shows three exemplary plots of the solubility temperature vs. the mass fraction. The letter z symbolizes mass fractions in any one- or two-phased mixture. The binary mixture formic acid/benzene has an upper critical solubility temperature whereas the mixture di-n-propylamine/water features a lower critical temperature. The third example system nicotine/water shows both a lower and an upper critical temperature. From these diagrams the concentrations of... 

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