A gram of liquid and vapor with heat of vaporization $L$ is carried around the very flat reversible cycle shown in Fig. 1.34. Beginning at point $A$, a volume $V_1$ of liquid in equilibrium with a negligible amount of its saturated vapor is raised in temperature by $\Delta T$ and in pressure by $\Delta p$ so as to maintain the liquid state. Then heat is applied at constant pressure and the volume increases to $V_2$ leaving a negligible amount of liquid. Then the pressure is lowered by $\Delta p$ and the temperature decreased by $\Delta T$ so that essentially all the material remains in the vapor state. Finally, heat is removed, condensing essentially all the vapor back into the liquid state at point $A$.
Consider such a Carnot cycle and write the change of boiling point with pressure, $d T / d p$, for the liquid in terms of the heat of vaporization and other quantities.
FIGURE CAN'T COPY.