BLASTING POWDERS. 513 



In Italy : 



Saltpetre 70 



Sulphur 18 



Charcoal 12 



What is called export trade powder in France, or strong 

 Hasting powder, contains 



Saltpetre 72 



Sulphur 13 



Charcoal 15 



2. There was formerly distinguished a class known as slow 



blasting powder : 



Saltpetre 40 



Sulphur 30 



Charcoal 30 



But the slowness of the reaction tended to diminish the effects 

 too much, and this powder is no longer in use. However, this 

 slowness may offer certain advantages for special uses, such as 

 the making of flying fuses, composed in the following manner : 



Powder dust 25O 



Saltpetre 44-5 



Sulphur 9-1 



Wood charcoal 2*4 



3. It was formerly supposed that blasting powder produces 

 a much greater volume of gases than that of service powder, 

 because it would be decomposed according to the following 

 equation : 



2KN0 3 + 6C + S = 600 + K 2 S + 2K 

 This equation would correspond to the proportions 



Saltpetre 65'5 



Sulphur 10-0 



Charcoal 24'5 



But observation has proved that it must be rejected, at least as 

 the fundamental representation of the reaction. 



It would produce, moreover, so little heat (74'5 Gals, per kgm., 

 p. 504), that the reaction could hardly propagate itself. 



4. Now, powder with an excess of charcoal deflagrates with 

 vivacity, and forms, like other powders, potassium sulphate and 

 carbonate, with a liberation of heat which is probably not far 

 remote from that of blasting powder for the same weight of 

 nitre consumed. A portion of the carbon tends, however, to 

 increase the proportion of carbonic oxide ; but a considerable 

 portion of the charcoal must remain intact. 



5. Hence, in this case, as in the foregoing, the sudden transfor- 

 mation of the explosive substance has a tendency to form the 

 products liberating the most heat, a remark of capital impor- 

 tance, and without which it would be difficult to understand 



2L 



