A slight addition of heat to the liquid at this state changes some of it into vapor. Saturated liquid line, SLL , is formed by connecting a series of boiling points.
Vaporization continues by further heat supply to the system until no liquid is left.
This state is known as dry saturated vapor, e.g. point 2. If the system is slightly cooled at this state, then droplets of liquid will begin to form. Connecting a series of points at dry saturated vapor builds a line, known as saturated vapor line, SVL . The state of substance between saturated liquid and dry vapor is called wet vapor. Further heating of a dry saturated vapor at constant pressure causes a rise of vapor temperature and it becomes superheated.