Clausius-Clapeyron Equation

The Clausius-Clapeyron equation relates the slope of the boundary line between two phases on a (p,T) plot to the heat of transformation of the phases, l12 ,their specific volumes, v1 and v2 , the temperature at which the transition occurs, T.

(dp12 /dT) = (l12 / T{ v2 - v1})

The phases 1,2 can represent (liquid, solid), (solid, vapor) or (liquid, vapor) with the corresponding heats of transformation being the heat of melting, the heat of sublimation, and the heat of vaporization, respectively.