3. The Detonation Process in Explosives 



3.1 Explosive Materials 



So far very little has been said about the explosive (the active cause 

 of explosions), except for assuming that unstable compounds, chemical 

 or otherwise, existed in which very rapid, violent reaction could be 

 started and, once started, maintain itself. The chemistry, mechanical 

 properties, testing, and production of such compounds is a very large 

 subject which can hardly be adequately summarized in the space of this 

 volume, let alone described in any detail.^ The complete omission of 

 such material would, however, be equally indefensible and the present 

 section attempts to give a qualitative picture of the information on ex- 

 plosives which is pertinent to an understanding of their effects under- 

 water. 



High explosives as a class nearly always contain oxygen which is 

 readily freed from its original molecule and made available for recombi- 

 nation with other atoms into more stable molecules. (That this is not 

 always true is evidenced by lead azide, Pb(N3)2, which contains no 

 oxygen at all but is a very sensitive and powerful material.) An explo- 

 sive reaction may thus be thought of as a breakdown of the original 

 molecules into product molecules (such as CO, CO2, H2O, NO, CH4, H2 

 as gases, and C, Pb, AI2O3 as solids) together with the evolution of 

 large amounts of heat of the order of a kilocalorie per gram of explo- 

 sive. Reactions of this kind can take place either as a process in- 

 volving initially a single reaction molecule or between dissimilar mole- 

 cules present in, say, a powdered mixture. The rate of reaction and 

 violence of the process will evidently be favored by the intimate prox- 

 imity in a single molecule of oxygen and other atoms with which it can 

 combine. Thus for high explosives, organic nitrated compounds are 

 used with a chemical formula of the form (CgHrOsN^, these molecules 

 being described as oxygen-rich or oxygen-deficient depending on whether 

 or not enough oxygen atoms are present to react with all the carbon and 

 hydrogen. Frequently metals such as Al, Pb in the form of powders are 

 incorporated in the material to react with the oxygen and increase the 

 heat involved, or conversely oxygen rich materials such as ammonium 

 nitrate, perchlorates, may be added to provide more oxygen. These 

 additions might therefore be expected to delay completion of the reac- 



^ An elementary account of the properties of explosives has been given by 

 Kistiakowsky (63), which includes discussions of detonation and burning, shock 

 waves, initiation, sensitivity, stability, and other properties. A number of books 

 discuss the chemistry of explosives, of which may be mentioned the works by Mar- 

 shall (71), Davis (25), and Meyer (73). 



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