ESDU AERO 00.01.12 introduces a large Mollier chart available separately that gives curves of speed of sound, pressure, density, temperature and real gas factor as functions of specific enthalpy and entropy. At temperatures where dissociation is present, it is assumed the air is in dissociation equilibrium and that the perfect gas laws apply to each component. Where appropriate the effects of the onset of liquefaction are taken into account. The data were extracted from three sources and relate to mixtures of nitrogen, oxygen, argon, carbon dioxide and, in one case, neon. Comparisons where the data overlapped demonstrated that the sources were in agreement. Constants appropriate to an argon-free atmosphere have been used for consistency with ESDU AERO 00.01.11. For temperatures between 2000 K and 13000 K, ESDU AERO 00.01.11 should be consulted and worked examples illustrating the use of the charts are in ESDU AERO S.00.03.27.