Fugacity: It is derived from Latin, expressed as fleetness or escaping ...

Phase Diagram for Binary solution
Constant pressure equilibrium
Consider a Binary system made up of component A and B. Where it is assumed to be
more volatile than B where vapour pressure ‘A’ is more than ‘B’. When the pressure is
fixed at the liquid composition can be changed the properities such as temperature and
vapour compositions get quickly determined VLE at constant pressure is represented on
T-xy diagram.
Boiling point diagrams
When temperature is plotted against liquid(x) and vapour(y) phase composition. The
upper curve gives and lower curve gives. The lower curve is called as bubble point
curve and upper curve is called as Dew point curve. The mixture below bubble point is
sub cooled liquid and above the Dew point is super heated vapour. The region between
bubble point and Dew point is called mixture of liquid and vapour phase.
Consider a liquid mixture whose composition and temperature is represented by
point ‘A’. When the mixture is heated slowly temperature rises and reach to point ‘B’,
where the liquid starts boiling, temperature at that point is called boiling point of whether
heating mixture reaches to point ‘G’ when all liquids converts to vapour the temperature
at that point is called as Dew point. Further heating results in super heated vapour. The
number of tic lies connects between vapour and liquid phase. For a solution the term
boiling point has no meaning because temperature varies from boiling point to Dew point
at constant pressure.