It then follows from eqn 1.18 that pVm ≈ RTB over a more extended range of pressures
than at other temperatures because the first term after 1 (that is, B/Vm) in the
virial equation is zero and C/V 2m
and higher terms are negligibly small. For helium
TB = 22.64 K; for air TB = 346.8 K; more values are given in Table 1.5.