DENSITY OF CHARGE AND SPECIFIC PRESSURE. 29 



(see p. 11), instead of remaining constant, as we have assumed 

 in our calculations. The dissociation, moreover, must be nil, or 

 reduced to the minimum for such considerable pressures. This 

 phenomenon does not enter into the question for nitrogen 

 sulphide, a compound resolvable into its elements by explosion. 



4. However this may be, this relation has been found to be 

 approached by Sarrau and Vieille in their researches on nitro- 

 glycerin and gun-cotton, substances furnishing no solid residue, 

 and such, moreover, that the products of their explosion are sus- 

 ceptible of dissociation. 



5. The experiments the author has made in common with 

 M. Vieille on nitrogen sulphide, and on mercury fulminate 

 under the conditions where the explosive substance is entirely 

 changed into gas, and, what is most essential into non-dis- 

 sociated gases, confirm it in a most positive manner. For 

 example, mercury fulminate having been taken with densities 

 of charge equal to 0'20 and 0*30, the results given by the 

 crusher, calculated according to the new estimate of the force of 

 calibration (forces de tarage), show for a density of charge equal 

 to unity (1 grm. in 1 cm.) 5915 kgms. according to the first ex- 

 periment ; 6233 according to the second (see pp. 26, 27), figures 

 which are sufficiently near each other for us to admit the verifi- 

 cation of the law. Similarly with nitrogen sulphide, for the 

 density of charge 0'30 we have found, from the indication of the 

 crusher calculated in the ordinary way, a pressure of 2441 

 kgms., which gives 8140 for the density 1. A second experi- 

 ment made with the density 0'2, which reduced to unity gives 

 8500 kgms., shows scarcely any deviation. 



Lastly, for gun-cotton, Sarrau and Vieille have found at 

 different densities of charge, figures fluctuating near a constant 

 value of about 10,000 kgms., according to their new theory. 



6. All these figures verify the approximate proportion between 

 the pressure developed and the density of charge. Some of 

 these have been calculated by means of the indications of the 

 crushers, according to the old method of estimating the forces of 

 calibration, and by simply deducing the pressure from the re- 

 maining height of the crushed cylinder. But it is easy to show 

 that the same practical verifications may be arrived at, at least 

 for high pressures, by the new theory of Sarrau and Vieille. 

 Let us first suppose the pressure equal to the force of calibration. 



= K + KE 



in the case of explosive substances of which the action is not 

 too rapid (p. 23) ; K and K being constants independent of 

 the explosive substance. Hence it results that for high pressure 

 the pressure tends to become proportional to s. The indications 

 based on the force of calibration calculated on the old system 

 retain, therefore, their signification in this case, and it is the 



