Applying the Clapeyron Equation to Other Kinds of Equilibrium

Poling et al. [8] use a five-constant vapor-pressure equation 

FIGURE 5.5 Comparison of the C-C and Antoine equations to the steam table vapor-pressure values over the range between the triple point and the critical point. 

7 APPLYING THE CLAPEYRON EQUATION TO OTHER KINDS OF EQUILIBRIUM 

As discussed in Section 5.2, the Clapeyron equation (but not the C-C approximation) applies rigorously to liquid-solid and solid-solid equilibria, as well as to the more common vapor pressure (vapor-liquid or vapor-solid) equilibria. We can also use it to compute the behavior of a phase change involving only solids and liquids. 

In most of the rest of this book we will use the Antoine equation and the constants in Table A.2. If we are writing a computer program for important calculations, the extra effort to program in Eq. 5.J and the correspondingly larger table of constants is probably worthwhile. In a few examples we will use the C-C equation, for reasons that will be clear in those examples. 

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