Clausius-Clapeyron relation

Upon a phase equilibrium curve

${\frac {dp}{dT}}={\frac {\Delta \left({\frac {S}{N}}\right)}{\Delta \left({\frac {V}{N}}\right)}}={\frac {\Delta S}{\Delta V}}$

where p is the pressure, T is the temperature, S is the entropy and V is the volume.