MERCURY FULMINATE. 469 



employed for discharging bullets in saloon arms. If placed in 

 a shell, and the latter can be projected by the aid of some 

 artifice of progressive expansion, the shell bursts at the striking 

 point, owing to the shock and heating resulting from the sudden 

 stoppage of the projectile. A hollow projectile is broken by. 

 fulminate into a multitude of small fragments, much more 

 numerous than those produced by powder, but which are not as 

 widely scattered. 



Its inflammation is so sudden that it scatters black powder 

 on which it is placed without igniting it ; but it is sufficient to 

 place it in an envelope, however weak, for ignition to take 

 place. The more resisting the envelope the more violent is the 

 shock, a circumstance which plays an important part in caps 

 and detonators. 



The presence of 30 per cent, of water prevents the decom- 

 position of finely powdered fulminate by friction or shock. 

 With 10 per cent, of water, it decomposes without explosion ; 

 with 5 per cent., the explosion does not extend beyond the part 

 struck. But these results are only strictly true for small 

 quantities of the substance, and it would be dangerous to attach 

 too much importance to them. 



Moist fulminate slowly decomposes on contact with the 

 oxidisable metals. 



7. The reduced volume of the gases produced by the decom- 

 position is 66'96 litres per 284 grms., or 235*6 litres per 1 kgm. 



If the mercury be supposed in the gaseous state, at a suitable 

 temperature t, we shall have 89*28 litres (1 -f at) per 1 equiv., 

 or per 1 kgm., 3141 litres (1 + at). 



235-6 atm. 



8. The permanent pressure = r~rr~- 



n 0'05 



6280 atm. 



9. The theoretical pressure = 



n 



The experiments which the author made with the crusher, in 

 common with M. Vieille, gave 



Density of charge O'l 480 kgm. 



' 0-2 1730 



0-3 2700 



9000 atm. 

 We should, therefore, have for high densities about - 



71 



But these figures should be reduced, in accordance with a more 

 exact estimation of the force of calibration (see p. 23). The 

 corrected calculation gives results very closely agreeing with 

 theory (p. 27), and leads to a specific pressure equal to 



'-. At the density 4'43, that is to say, the fulminate 



n 



exploding in its own volume, we should have, therefore, 



