Temperature vs. pressure for pure component
These results are conveniently presented in graphic form using several types of "phase diagrams."
If the data are taken with pressure held constant (isobaric), it is convenient to plot two curves on the same paper: temperature versus x and temperature versus y. Figure 2.7 illustrates a typical T-xy diagram. To determine the composition of liquid and vapor phases in equilibrium with each other at a given temperature, and at the pressure under which the data were obtained, one merely draws a horizontal line at the given temperature and reads off x and y values.
Data taken at constant temperature (isothermal) are plotted as two curves: pressure versus x and pressure versus y, as illustrated in Figure 2.8. Note that the ends of the curves must intersect at x = y = 0 and at x = y = 1, since these points correspond to pure components, either light or heavy.
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