3. Clapeyron equation and pure-body VLE

3.1 ELV condition

Consider a pure compound in liquid-vapor equilibrium at temperature T (T Î [T _tr , T _C ]). By definition, the system pressure is p ^s (T ), i.e. the saturation vapour pressure of the compound in question at temperature T. When thermodynamic equilibrium is reached, there is no heat transfer, no exchange of volumetric work and no transfer of matter between the two phases.

For thermal equilibrium to be achieved, i.e. for there to be no heat transfer between the two phases, it is necessary and sufficient for the temperature T to be uniform throughout the system: