Given that IAST calculations are performed using numerical quadrature to compute the spreading pressure, it is important to understand how "extrapolating" beyond the last pressure point using pyIAST affects the mixture predictions. On the right-hand side of Figure , we consider a complete pure component isotherm (red line), which is then truncated at P cut . pyIAST is used to extrapolate the resulting incomplete isotherm (blue line) as described previously. The shaded area corresponds to the integration difference between the complete and incomplete isotherms and can be described by: