AbstractExothermic reactions of some self igniting fuel‐HNO3 systems have been examined by the rapid‐scan FIR/thermal profiling technique. A sudden rise in temperature is observed when the liquid oxidizer is dropped onto the solid fuel. Simultaneous monitoring of the gas products of the reaction occurring between p‐phenylenediamine and HNO3 reveals the formation of Co2, NO2 and HONO. Immediate evolution of NO2 is observed in the synergistically igniting systems comprised of substituted anilines, Mg and HNO3. Thiocarbohydrazide and its acetone and benzaldehyde monoderivatives on reacting with HNO3 produce SO2, NO2 and, possibly, OCS. The results are explained in terms of the oxidation and nitration reactions occurring in these systems.