“…If PVT data are of sufficiently high precision, a distinction between trimer and tetramer can be made with eq 3. If, in a vapor mixture, species of molecular weight higher than the trimer are not present, eq 3 (by setting fa = 0) reduces to fa' -2fa2p3 = fa + 2fap (4) Likewise, if the trimeric species is taken as insignificant, the same equation reduces to fa' + 2 fafap3 = fa + Sfap2 (5) It follows from these equations that a linear relationship between (fa' -2fa2p3) and p implies the existence of trimer, while a linear relationship between (fa' + 2fafap3) and p2 implies the existence of tetramer.…”