512 POWDERS WITH A NITRATE BASE. 



8. SPORTING POWDER. 



1. Sporting powder is distinguished from service powders 

 principally by the surplus proportion of saltpetre and by the 

 choice of the charcoal. 



The following are the proportions adopted in France : 



Saltpetre 78 



Sulphur 10 



Charcoal 12 



2. The rapidity of inflammation of sporting powder is less, 

 according to Piobert, than that of service powder, being in 

 proportion to the coarseness of the grains. For a sporting 

 powder containing 30,000 grains to the gramme, the rapidity of 

 the inflammation was 0'30 m. per second ; while for a service 

 powder containing 259 grains to the gramme, the rapidity 

 amounted to 1-52 m. 



The rapidity of combustion is also checked by the surplus 

 proportion of saltpetre. It amounted to 8 mm. to 9 mm. per 

 second in Piobert's experiments ; while for service powder this 

 writer found 10 mm. to 13 mm. 



3. Brown charcoal tends to give powder shattering properties 

 because it increases the heat liberated owing to the special com- 

 position of this charcoal. 



4. The surplus proportion of saltpetre also increases the heat ; 

 but it diminishes the volume of the gases, as is shown by the 

 figures on page 491, compared with those on page 503. 



5. If the heat liberated be supposed proportional to the 

 weight of the saltpetre, which should not be far from the truth, 

 the heat will be greater by about a twenty-fifth for sporting, 

 than for service powder, weight for weight. Now, the experi- 

 mental data are not greatly at variance with this calculation. 

 On the other hand, the permanent gases will diminish, which 

 also agrees with Noble and Abel's results. Hence a certain 

 compensation is afforded by it. Owing to this fact there is 

 little difference between the strength of sporting and that of 

 service powder. 



9. BLASTING POWDERS. 



1. Blasting powders present very varying proportions. The 

 principal object aimed at is to increase the volume of the gases ; 

 which is attained by the diminution of the saltpetre, and the 

 increase of the sulphur and charcoal. It is also sought to 

 dimmish the cost of this powder. 



The following are the proportions adopted in France : 



Saltpetre 62 



Sulphur 20 



Charcoal 18 



