CHAEACTEEISTIC PBODUCT." 33 



V Q 



nc 



3. In the case where there exist along with the gases fixed 

 substances, so that the unit weight of the explosive substance 

 yields a quantity of fixed substance occupying a fraction of a 



V 



cub. cm., a, it will be necessary to replace -2-X- by 



nc 

 V.Q 



(n a)c 



4. The expression which has just been defined is almost 

 exactly proportional to the theoretical pressure for any two 

 explosive substances capable of being entirely changed into gas 

 at the temperature of the explosion. 



Now, for a given substance, the theoretical pressure is given 

 by the expression 



If the temperatures were reckoned from the absolute zero this 

 expression would become 



V Q 



that is to say, that it would be identical, with the exception of 

 a multiple, with the characteristic product. 



For another substance, enclosed in the same capacity, under 

 the same density of charge there will be 



an expression which would become from the absolute zero 



V'oQ' 



273^' ' 



In reality action takes place at an initial temperature higher 

 than the absolute zero; but it should be noted that if the 



quotient ^ represents a number much greater than unity, 



the ratio of the theoretical pressures for two given substances, 

 that is 



