Observations on the Reactivity of Pyrotechnic Compositions containing potassium chlorate and thiourea

An explosion occurred recently during the operation of a grinder that had been used to process potassium chlorate and then thiourea. As part of our investigation of this accident we determined the mechanical sensitiveness of mixtures containing these components and showed that they can be very sensitive to both impact and friction stimuli. Thermo‐analytical studies indicate that the binary mixture can react at up to 200°C below the melting point of the oxidizer; the exothermic process is characterized by a high reaction energy. Temperatures of ignition of the mixtures were less than 155°C, whereas the individual components gave no ignition below 400°C.