PRODUCTS OF COMBUSTION. 495 



of saltpetre. On the other hand, they yield a much greater 

 volume of gas, which compensates, so that the strength of such 

 a powder is after all superior to that of a total combustion 

 powder. It will be seen that this fact must introduce some 

 complication into the chemical reactions. 



3. The latter, moreover, change greatly in character with the 

 pressure, when operating in a closed vessel. They are also 

 modified during the discharge of firearms owing to the rapid 

 expansion of the gases. But the analytical experiments then 

 become very delicate owing to the difficulty of collecting the 

 products, and preventing them from undergoing at this moment 

 the oxidising action of the air, which is the more to be appre- 

 hended, the more divided the pulverulent products are. 



4. Let us now go into detail. Observation shows that the 

 combustion of powder produces as principal products the follow- 

 ing bodies (neglecting certain accessory substances to which we 

 shall return later on) : 



Potassium carbonate, sulphate, and sulphide, or rather, 

 poly sulphide, carbonic oxide, and nitrogen. 



There subsists no sulphurous acid, nor carbon, nor oxygenated 

 compounds of nitrogen, whether free or in the saline form 

 (except sometimes some nitrite). 



5. These results are accounted for in the following way. At 

 first the salts of the lower oxygenated acids of sulphur and 

 nitrogen are all decomposed by the high temperature of the 

 explosion. As for sulphurous and hyponitric acids, they are 

 reduced by the carbon and carbonic oxide (see p. 480). 



6. Nevertheless, some traces of accessory products are obtained, 

 such as water, ammonium carbonate, potassium hyposulphite, and 

 sulphocyanide, sulphuretted hydrogen, hydrogen and methane ; 

 all these bodies being due to secondary reactions, or reactions 

 developed during cooling. We shall presently return to them. 



7. We have now to examine the relative proportions of the 

 various products. We shall first define the initial state. 



8. Initial state. The analyses were made on powders, the 

 composition of which was nearly the following : 



Saltpetre 74-7 



Sulphur 10-1 



Charcoal 14-2 1 



Water 1-0 



These numbers, taken roughly, approach the following relations : 



16KN0 3 + 21C + 7S, 

 in the vicinity of which the composition of the powder of the 



1 The charcoal used contained in 14-2 parts : pure carbon, 12'1 ; hydrogen, 

 0'4 ; oxygen, 1-45 ; ashes, 0'2. 



Nitre 772-5 



Carbon 120'5 



Sulphur 107 



