The initial stages of explosion in nitroglycerine

Abstract

The sequence of events which occurs in a thin confined film of nitroglycerine, after an explosion is initiated by a condenser spark, has been examined by means of a rotating drum camera. It has been found that in a very thin film (< 0⋅01 mm. thick) the explosion begins as a gentle process which is propagated through the nitroglycerine film at 400 m./sec. After continuing for about 0⋅5 cm. this process is transformed suddenly to a more violent type of explosion which is propagated at 2000 m./sec. The explosion reproduces in miniature several of the well-known effects characteristic of the setting up of the detonation wave in gaseous mixtures. When explosion is initiated in the same manner in a thicker film, the 400 m./sec. type of propagation is not set up immediately but is preceded by a very much faster process (5000 m./sec.), which after propagating for a few millimetres is transformed into the normal 400 m./sec. process. Subsequent to this transformation the propagation continues exactly as in the very thin films. It is suggested that, under conditions of impact initiation, the propagation of the explosion through the film of nitroglycerine between the hammer and the anvil takes place in a manner closely similar to that which obtains after initiation by spark.