APPENDIX. 553 



If a larger quantity, not more, however, than a few centigrams, 

 be used, the bottom of the tube may be sufficiently cooled to pre- 

 vent immediate detonation, but the picric acid will be vaporised 

 and a less violent explosion, accompanied with flame, will soon 

 take place. 



With a decigram of the acid the action is slower, but the sub- 

 stance soon fuses and deflagrates with vivacity. Finally, if the 

 quantity be still further increased, the acid decomposes without 

 deflagration. 



Similar experiments were also made on other nitro compounds, 

 and it was found that nitrobenzene, dinitrobenzene, mono-, di-, and 

 trinitronaphthalene all detonated under the conditions of the 

 experiments, while giving rise to different modes of decomposition 

 when the quantities were increased. 



These varied modes of decomposition l depend on the initial 

 temperature of decomposition. 



If the surroundings be of sufficient mass to absorb the heat 

 produced there will be neither deflagration nor detonation. If, 

 however, a large mass of a nitro compound like picric acid while 

 burning heats the walls of the vessel containing it sufficiently to 

 start deflagration, this will still further heat the containing vessel, 

 and the phenomenon may develop into detonation. 



It would suffice, if this happened at an isolated point, through a 

 fire or any local superheating, to start the explosive wave, which 

 would be propagated through the entire mass, and thus give rise 

 to a general explosion. 



1 Compare the different modes of decomposition of ammonium nitrate, p. 5. 



