454 GUN-COTTON AND NITRO-CELLULOSES. 



same weight of dry gun-cotton with 20 per cent, of added 

 water. It is 1038 Cal. with only 10 per cent, of added water. 

 This makes, in other terms, for 1 kgm. of the damp substance 

 containing 16*7 per cent, of water, 662 Cal., and for 1 kgm. of 

 the substance containing 91 per cent, of water, 882 Cal., the 

 whole of the water being supposed gaseous. The heat is there- 

 fore reduced by a fifth in the latter case, and by a third in the 

 former, owing to the vaporisation of the added water. 



5. The volume of the reduced gases will be for 1 kgm. of the 

 dry substance, with 20 per cent, of added water, 1563 litres ; 

 or 1139 litres for 1 kgm. damp. 



We shall have further, for 1 kgm. of dry matter with 10 per 

 cent, of added water, 1272 litres ; or 1133 litres for 1 kgm. of 

 the damp substance. 



The gaseous volume is therefore increased by the addition 

 of water, as might be expected, supposing vaporisation to take 



place. 



391 kgm. f 



6. The permanent pressure = - for the substance 



7t Uol 



with 20 per cent., and -f - with 10 per cent, of water 

 n 0'2o 



added, with the usual reservations regarding the limits of 

 liquefaction of carbonic acid. 



7. The theoretical pressure = - for the substance 



n 



with 20 per cent., and ' with 10 per cent, of added 



n 



water. It will be seen that it is diminished by a third in the 

 latter case, and that it is reduced almost to the half in the case 

 of the most hydrated substance. 



8. Paraffined gun-cotton. Instead of adding water to gun- 

 cotton it has also been proposed to paraffin it, which yields 

 mixtures which are more stable and even capable of being cut 

 arid wrought by tools working at high speeds. But it is 

 difficult to render them uniform, unless by adding so great a 

 quantity of paraffin that the mixture only explodes with great 

 difficulty; 100 parts of gun-cotton absorb as much as 33 of 

 paraffin. 



Hence the operation is often confined to paraffining the 

 cartridges superficially. To explode paraffined gun-cotton an 

 auxiliary cartridge of ordinary gun-cotton is employed, ignited 

 by a fulminate detonator. 



9. The use of camphor and plastic substances diminishes still 

 further the liability of gun-cotton to explode. We may also 

 mention here celluloid, a variety of nitro-cellulose, nearly 

 corresponding to C^H^NOaH)^, to which camphor and 



