PKOJECTTLES CONTAINING EXPLOSIVES A. R. 



133 



Finally, the definition of an explosive from the point of view under 

 consideration is completed by a knowledge of its aptitude for deto- 

 nation which is evidenced by its sensitiveness to the blow of a ham- 

 mer of given mass (20 to 30 kilos) falling from a determined height, 

 or by its sensitiveness to detonation by a detonator containing a 

 given weight of mercury fulminate. 



The following table gives the values for the force and potential 

 pertaining to commonly occurring explosives: 



F. 



(1) Gunpowder 



(2) Mercury fulminate 



(3) Ammonium nitrato 



(4) Ammonium picrate 



(5) Ticric acid 



(6) Cellulose endecanitrate (guncotton) 



(7) Cellulose octonitrate (collodion cotton) 



(8) Nitroglycerin 



It may be said concerning the velocity of detonation that it attains 

 its maximum value with crystalline bodies such as picric acid and 

 nitromannite where it is of the order of 7,000 meters per second and 

 falls to about 2,500 meters in liquid and plastic substances such as 

 nitroglycerin and d}aiamite. 



If we designate by A the value of the ratio <p/(7 where cp represents 

 the weight of explosive contained in volume C and a the covolume 1 

 of the mass of gas produced in the explosion (that is to say, the 

 volume limit occupied by this gas under an infinite pressure), Noble 

 and Abel have shown that the pressure, P (in kilos per sq. cm.), 

 developed under these conditions on the walls of a receptacle G was 

 defined by the formula 



p.. /A J__ 



1-aA 1 



When the density of loading A becomes equal or superior to 1/a, the 

 denominator of P becomes zero, and the pressure is infinite. Ee- 

 sistant as the envelope containing the explosive may be, it is then 

 ruptured and the debris projected. 



The interior of a projectile being supposedly filled with the ex- 

 plosive constituting the charge if its density is greater than 1/a the 

 preceding conditions are evidently fulfilled. 



1 Sarrau has shown that the value of a is for all gases very nearly V/1000. 

 65133°— sm 1917 10 



