SERVICE POWDER. 493 



(1) General Properties of Powder. 



1. The proportion, " six, ace and ace," that is to say 



Saltpetre 75'0 



Sulphur 12-5 



Charcoal 12-5 



has never been far departed from in France. An excess of char- 

 coal and of nitre increases the strength ; an excess of sulphur 

 has been found favourable to the preservation of powder. The 

 presence of sulphur, moreover, lowers the initial temperature of 

 the decomposition of the substance and regulates it. The 

 actual proportions in France are 



Nitre. Sulphur. Charcoal. 



Ordnance powder 75 12'5 12-5 



Old coarse grained powder ... ... 75 10 15 



Rifle powder, Class B 74 10'5 15-5 



Rifle powder, Class F 77 8 15 



Austria 75'5 10 14-5 



United States, Switzerland 76 10 14 



Holland 70 14 16 



China 61-5 15-5 23 



Prussia 74 10 16 



England, Russia, Sweden, Italy 75 10 15 



The composition 75, 12*5, 13*5, corresponds practically to the 

 relations 



2KN0 3 -f S + 30, 



or 101 -f 16 +18 ; in all, 135 grms. ; or, for 1 kgm., 748 grms. of 

 saltpetre, 118*5 grms. of sulphur, and 133*5 grms. of carbon. 



2. The temperature of inflammation of powder was fixed at 

 316 by Horsley. This temperature varies with the process of 

 heating. It may fall to 265, according to Violette. 



If the heating takes place slowly, the sulphur melts, causes 

 the aggregation of the grains, then gradually vaporises and 

 may even be almost entirely sublimed. The nature of the 

 charcoal has great influence in this case ; some wood charcoals 

 yielding carbonic acid on contact with the air at 100 and even 

 below p. (489). 



It is, therefore, natural to suppose that such charcoals, if their 

 surface be not completely covered by sulphur and saltpetre 

 through a very intimate mixture, may become more and more 

 rapidly oxidised at a temperature which moreover goes on 

 increasing owing to the oxidation. They may even take fire, 

 especially if the mass be so large that the heat produced by 

 this oxidation has not time to dissipate itself. We may in 

 this way account for certain accidents caused by spontaneous 

 inflammation of heaps of powder dust. 



3. The inflammation of powder is caused by the shock of 

 iron on iron, iron on brass or marble, brass on brass, quartz on 

 quartz, less easily by iron on copper, or copper on copper. It 



