Lastly, in the bottom pane, we consider the case of assuming ∆Z vap = 1 and assuming ∆H vap /R is constant. For the value of ∆H vap /R we again use the value at the lowest temperature (the triple point, min), the average value (avg) and the average (natural) log value (Lavg), and the value at the highest temperature (0.097 K below the critical point, max). Interestingly, the best set of predictions is made using the value at the triple point. At the triple point, the assumption that ∆Z vap = 1 is reasonable, and we find that the predictions using a constant value of ∆H vap / (R∆Z vap ) and ∆H vap /R at the triple point are indistinguishable from each other. The other predictions noticeably diverge from the reference data, with the predictions worst using the value of ∆H vap /R at the highest temperature the assumption that ∆Z vap = 1 is least appropriate.