In the two phase region this function returns the interpolated heat capacity between the liquid and vapour state heat capacities.
function specificHeatCapacityCp_pTX_liq_Francke input SI.Pressure p; input SI.Temp_K T; input SI.MassFraction X[:] "mass fractions m_i/m_Sol"; input SI.MolarMass MM_vec[:]; output SI.SpecificHeatCapacity cp; end specificHeatCapacityCp_pTX_liq_Francke;