We have established the locus of thermodynamic states encountered in SDF explosions. For the detonation products gases, the locus is a composite CJ isentrope (with fixed composition below 1,800 K and equilibrium composition above 1,800 K). For the combustion products, the locus is the 10-bar equilibrium isobar. By CHEETAH code calculations we have proven that both the Detonation Products and the Combustion Products behave as calorically-perfect gases for temperatures below 3,500 K.