426 NITRIC ETHERS PROPERLY SO CALLED. 



heat of silica be supposed constant and equal to 0*19, which 

 makes for 73*7 grms. of silica 14'4, the theoretical temperature 

 becomes 



335600 _ 



62-4 



The corresponding pressure will be 

 / 8378\ 

 V + ~273~) _ 14759 atm. 15281 kgm. 



n n n 



a value higher by a third than the actual figure found for high 

 densities. 



14 To sum up weight for weight nitroglycerin produces 

 three and a half times as much permanent gases reduced to 

 as nitrate powder, and twice as much as chlorate powder. 



At equal volumes it produces nearly six times as much 

 permanent gases as ordinary powder. As, moreover, it produces 

 weight for weight more than double the heat, the difference 

 between the effects of the two substances taken in equal 

 weights is easy to foresee. 



At equal volumes this difference is still greater. Thus 

 one litre of nitroglycerin weighs 1'60 kgm., whilst one litre of 

 ordinary powder weighs about 0*906 kgm. At the same volume 

 as powder, nitroglycerin will develop a pressure ten or twelve 

 times greater ; which may be actually realised in a completely 

 filled capacity, as in the case of a blast-hole, or when operating 

 under water. Under these conditions the maximum work 

 developed by one litre of nitroglycerin may amount to a value 

 treble that of the maximum work of ordinary powder at the 

 same volume. These colossal figures, no doubt, are never 

 attained in practice, especially owing to phenomena of dis- 

 sociation, but the fact that they are approached is sufficient to 

 explain why the work, and especially the pressures developed 

 by nitroglycerin, exceed the effects produced by all the other 

 explosive substances industrially employed. The relations 

 which these figures show between nitroglycerin and ordinary 

 powder, for example, agree pretty closely with the empirical 

 results observed in the working of mines. 1 



15. The rupture into fragments and the explosion of wrought 

 iron, 2 effects which cannot be produced by ordinary powder, 



1 See the experiments cited in the small treatise " La Dynamite," by Trauzl, 

 extracted by P. Barbe, pp. 91 and 92 (1870). The usual effect of nitro- 

 glycerin in quarries has been found to be five or six times greater than that, 

 of blasting powder, weight for weight. For an equal volume in blast-holes, 

 there is obtained with dynamite about eight times the effect produced by 

 powder ; that is to say, eleven times the same effect for a given weight of pure 

 nitroglycerin employed under this form. This refers to effects of dislocation, 

 which depend especially upon the initial pressures. 



2 Same work (pp. 98 and 99). 



