472 DIAZO COMPOUNDS AND OTHERS. 



8. Let us compare these theoretical results with the experi- 

 mental measurement of the pressures. M. Vieille and the 

 author obtained with a crusher the following figures : 



Density of Weight of Pressures in k^ms. 



charge. the charge. per square centimetre. 



0-1 ... 2-37 grins. ... 990 kgm. 



0-2 ... 4-74 ... 2317 



0-3 7-11 ... 4581 



In the last experiment made with diazobenzene nitrate, this 

 body filled the whole of the vacant space, and the steel tube 

 was cracked. This points to local effects, which may have 

 slightly affected the results. The recent researches of Sarrau 

 and Vieille on the calibration of the " crushers " tend to 

 reduce by half the absolute value of the pressures for substances 

 having so sudden an explosion, but without changing the 

 relations. 



In any case, the pressures of diazobenzene nitrate are far higher, 

 actually and theoretically, for the same density of charge, than 

 those developed by the explosion of mercury fulminate. On 

 the contrary, the fulminate exploding in its own volume would 

 develop a far greater pressure (28750 kgm., instead of 7500 

 kgm.), owing to its great density. 



The great activity of diazobenzene nitrate, in any case, renders 

 it more dangerous. 



6. NITRIC ACID ASSOCIATED WITH AN ORGANIC COMPOUND. 



1. It has been seen in Chapter III. (p. 396), how the liquefied 

 oxygenated gases, especially nitrogen monoxide and nitric per- 

 oxide, when mixed with combustible liquids, form explosive 

 substances of a very special character. It has been proposed 

 to prepare similar substances by mixing nitric acid with com- 

 bustible organic substances. In case of need the mixture may 

 be made on the spot, the ingredients being separately conveyed ; 

 it is exploded by a fulminate cap. This is the principle of 

 Sprengel's acid explosive. In practice, the substances capable 

 of being mixed with nitric acid are few in number, owing to the 

 violent oxidising action exerted by this acid on the greater 

 number of organic substances. Few liquids can be mixed with 

 it without being attacked, and the pastes formed by imbibition 

 are also subject to reaction. 



In fact, only two mixtures of this kind have been employed, 

 or rather, specially prepared the mixture of picric acid (solid) 

 and nitric acid, which forms a paste ; and the mixture of nitro- 

 benzene and the same acid, bodies which dissolve each other 

 reciprocally. It will be seen that it is two already nitrified 

 bodies which serve as base to the mixtures ; further, that the 

 second would soon be transformed into crystallised dinitro- 



