AMMONIA AND NITRIC OXIDE. 65 



mixture be raised, then the sulphur should burn in nitric 

 oxide. 1 



This is what is noticed, as we know, in operating with 

 sulphur placed in a small crucible previously brought to a 

 red heat. 



The temperatures of combustion estimated in this way are 

 generally very near those estimated by the employment of free 

 oxygen, the excess of heat produced by the decomposition of 

 nitric oxide being compensated by the necessity of heating the 

 nitrogen. All these figures, however, do not express absolute 

 values, yet they may be regarded as marking the relative order 

 of temperatures of combustion. 



12. This table, understood in this manner, shows that the 

 property of burning at the expense of nitric oxide under the 

 influence of a flame or electric spark, depends more especially 

 on the temperatures developed. The comparison of ethylene 

 with methylic ether is particularly decisive in this respect, 

 since the relations of volume between the combustible and the 

 combustive gas are exactly the same, and the heats disengaged 

 (451,100 cal. and 443,800 cal.) do not sensibly differ, but 

 methylic ether also contains the elements of water, which lowers 

 the temperature of combustion. 



In short, among the bodies comprised in the table, none of 

 those which develop a theoretical temperature below 7000 will 

 ignite, whereas all the bodies which develop a higher tempera- 

 ture either burn or detonate. It is possible that this circum- 

 stance is connected with the previous formation of nitric 

 peroxide at the expense of nitric oxide (see p. 62), and con- 

 sequently with the necessity for a very high temperature in 

 order to regenerate, at the expense of the nitric oxide, the 

 oxygen which is indispensable to combustion. 



13. Instead of destroying nitric peroxide by heating it to an 

 excessively high temperature, it can be decomposed by a 

 chemical reaction at a lower temperature, which lowers the 

 theoretical limit of the temperature of combustion. 



This is precisely what happens in the case of ammonia gas. 

 This gas, in fact, mixed with nitric oxide, 



3NO + 2NH 3 , 



ignites with a match, and, according to W. Henry, detonates 

 under the influence of the electric spark. The theoretical 

 temperature of combustion of the mixture (5200) is, however, 

 less than all the foregoing temperatures. But, on the other 

 hand, nitric peroxide reacts even when cold on ammonia gas, 

 and the reaction develops itself still more simply by the intro- 

 duction of oxygen into a mixture of nitric oxide and of ammonia 

 gas. When cold it will produce both nitrogen and ammonium 



1 "Essai de M^canique Chimique," torn. i. p. 331. 



F 



