The point that connects the saturated liquid line to the saturated vapour line is called _______. 

Explanation:

At critical point saturated liquid and saturated vapor point coincide. No distinct phase can be made in two phases. The latent heat of vaporization is zero at a critical point.

Pcr = 220.6 bar = 22.06 MPa

Tcr = 373.95oC

vcr = 0.005155 m3/kg

At a critical point, the liquid is directly converted into vapor without having a two-phase transition. So, enthalpy of vaporization at a critical point is zero. 

The figure below represents the P-V diagram for a pure substance (water).

Additional Information

Triple point of a substance is the temperature and pressure at which the three phases (gas, liquid, and solid) of that substance coexist in thermodynamic equilibrium.

• The triple point is merely the point of intersection of the sublimation and vaporization curves.
• It has been found that on a ‘p-T’ diagram the triple point is represented by a point and on a ‘p-v’ diagram it is a line, and on a ‘u-v’ diagram it is a triangle.
• In the case of ordinary water, the triple point is at a pressure of 4.58 mm Hg or 611.657 Pa and a temperature of 0.01°C or 273.16 K.