104 CHEMICAL PROPERTIES AND* COMPOSITION 



importance or not. The first includes explosive materials 

 that are solid or liquid, the latter those that are gaseous. 

 In the former group, which includes gunpowder, the factor 

 y 



= alone is something like one thousand, in the latter, e. g. 

 "i 

 oxyhydrogen mixture, mostly near unity, and may be less, 



as in the instance mentioned where it is two-thirds ; hence 

 in the former case the pressure may be thousands of atmo- 

 spheres, in the latter from a few up to twenty, mainly on 

 account of the factor ( i -f t)> The explosives used in 

 practice therefore belong exclusively to the first category, 

 i. e. are solids or liquids which form gases with a consider- 

 able evolution of heat. 



We may now go over the various bodies in question, with 

 reference to their composition and the connexion between 

 constitution and explosibility, beginning with the simplest, 

 we get the following scheme : 



(a) Simple explosives. 

 (&) Explosive mixtures. 

 (c) Practical explosives. 



(a) Simple Explosives. 



First, we will bring together the simpler bodies that are 

 capable of reaction with evolution of heat, whether actual 

 explosion takes place or not. The main condition for an 

 explosion is then given, and it has only to be considered 

 what conditions bring it to pass. 



The first element to consider which plays such a part is 

 ozone (O 3 ), which, in the liquid state, is capable of explosion 

 with formation of oxygen (O 2 ) with an evolution of heat 

 that amounts to 36 calories for the gas, per 48 grams (O 3 ) 

 of material. 



Next in simplicity come the binary compounds, of which 

 a list is appended, with the heat of formation of each from 

 its elements : 



