WET GUN-COTTON. 453 



4. WET GUN-COTTON. 



1. We have explained how it has been found advisable to 

 employ gun-cotton saturated with water, in order to lessen its 

 sensitiveness to shock and to render its direct inflammation 

 impossible, which limits the risks due to a fire. Three per 

 cent, of water is sufficient to diminish the sensitiveness, but 

 more than 11 per cent, is required to prevent direct inflamma- 

 tion. The standard quantity is 15 per cent, of water; but it is 

 difficult to maintain constant and uniform in the whole mass. 

 Thus regular saturation, followed by compression, leaves about 

 25 per cent, of water in the mass, which renders a partial 

 drying necessary. Besides, the moist substance, if it be not kept 

 in hermetic receptacles, tends to lose the water by spontaneous 

 evaporation. 



2. Damp gun-cotton retains the property of exploding under 

 the influence of a powerful fulminate detonator, or of a small 

 intermediate cartridge of gun-cotton dry, or mixed with nitrate, 

 with fulminate cap. Thus a torpedo containing 100 kgm. of 

 gun-cotton requires a priming cylinder containing 0'560 kgm. 

 of dry gun-cotton. It will be useful to examine the influence 

 of the water thus introduced on the pressures developed. 



3. Granted that the chemical reaction is the same as with 

 high densities of charge (which, however, has not been verified), 

 the heat liberated remains the same. The volume of the gases 

 produced by gun-cotton also remains the same, whether it be 

 calculated from that of the permanent gases alone, or the water 

 derived from the gun-cotton be supposed to retain the gaseous 

 state at the first instant of the explosion ; an hypothesis which 

 the experiments made on the explosive wave (p. 99) justify us 

 in regarding as possible. Condensation will, moreover, take 

 place almost immediately ; the water vapour thus ceasing to be 

 active beyond the first instant. 



Nevertheless, the water imprisoned in gun-cotton also absorbs 

 heat, and may even be regarded as assuming, either wholly or 

 partly, the gaseous state, simultaneously with the water pro- 

 duced by the reaction. 



We will calculate the pressure developed at the moment of 

 explosion according to the various hypotheses. 



4. Take, for example, gun-cotton with the addition of 20 per 

 cent, of water 



C ai H 18 (N0 3 H) u 9 + 26H 2 0, 



and gun-cotton with 10 per cent, of water 

 C 24 H 18 (N0 3 H) U 9 + 13H 2 0. 



The heat liberated by decomposition with a high density of 

 charge will be 1168 Cal. (water gaseous), or 1022 Gal., for 1 

 kgm. of the dry substance. This heat falls to 908 Cal. for the 



