458 GUN-COTTON AND NITRO-CELLULOSES. 



consequently of oxygen. It corresponds to a liberation of 

 2240 Cal. (carbonate, gaseous water), or 2560 Cal. (bicarbonate, 

 liquid water). Or for 1 kgm. of the substance, 980 Cal. or 

 1120 Cal. Sarrau and Vieille found 954 Cal. for a substance 

 of this order ; but, in reality, the combustion in their experiment 

 did not give rise either to the total destruction of the nitrate, or, 

 probably, to the integral and immediate change of the carbonate 

 into bicarbonate. 



4. The volume of the reduced gases will be, according to 

 equation (1), 1062*5 litres (carbonate and gaseous water) or 728 

 litres (bicarbonate and liquid water) ; or, for 1 kgm., 475 litres 

 or 271 litres. 



Sarrau and Vieille found only 196 litres ; a figure which is 

 too low, for the reasons given above. 



5. Owing to these considerable differences between the 

 theoretical and the real equation, it appears useless to calculate 

 the theoretical pressure of this powder. We will only mention 

 that Sarrau and Vieille found, by the crusher process, operating 

 on the product containing an excess of nitre 



Density of charge. Pressure. 



0-20 1315 kgm. 



0-30 3100 



0-40 4900 



0-50 5520 



values which are nearly the half of those given by pure gun- 

 cotton or the same mixed with ammonium nitrate. 



6. This is, moreover, what theory would enable us to fore- 

 see in a general way. 



In fact, 1 kgm. of gun-cotton, decomposed under a high 

 pressure, develops 859 litres and produces 1020 Cal. (water 

 gaseous). On the other hand, 1 kgm. of gun-cotton mixed with 

 ammonium nitrate develops 862 litres and produces 1120 Cal. 

 (water gaseous). Whilst 1 kgm. of gun-cotton mixed with potas- 

 sium nitrate can only develop 475 litres and produce 980 Cal. 



The volume of the gases with the latter mixture is therefore 

 nearly half that produced by the two other substances, the heat 

 being slightly less. Consequently the pressures will fall to 

 about the half for the same density of charge. Dissociation, 

 moreover, will intervene to lower the initial pressure and 

 moderate the fall of the successive pressures. 



7. On the whole, theory does not show that the addition of 

 potassium nitrate to gun-cotton, which is rather inconvenient 

 to realise in practice, offers any very great advantages, except 

 in the way of economising the gun-cotton, rendering expansion 

 less abrupt and suppressing the carbonic oxide. The experi- 

 ments which have been made with similar mixtures formed of 

 various nitrocelluloses impregnated with potassium nitrate 

 seem to point to this conclusion. 



