PVT Projections

Projections of the (pvT)
surface onto the (p,T) plane
(a) and the (p,v) plane (b)
are show opposite. In (a)
the lines separating the
phases are projections of
the two-phase surfaces onto
the (p,T) plane. Points on

these lines describe the condition for which the two phases have the same Gibbs function. The line between the liquid and gas phases starts at the Triple Point and ends at the Critical Point. The line between the solid and liquid phases also starts at the triple point but continues to arbitrarily high pressure. The (p,v) projection shows the single and two phase regions. The line passing through the Critical Point is the Critical Isotherm. Above T_cr , liquid and vapor are indistinguishable.