The pseudocomponents are "lumps" of components (usually heavy ends) and the critical properties of the psuedocomponents are determined in the lab. I need to calculate ideal gas heat capacity/enthalpy for the "lump" to get to the enthalpy departure. I think the GPA has some sort of correlation to predict the ideal properties from the critical properties and the MW but I can't remember where to find it. It may be a "senior" moment or a "blonde" moment but I'm stumped at the moment.