02 DURATION OF EXPLOSIVE REACTIONS. 



into its elements ; for this decomposition takes place at from 

 500 to 550, according to the author's experiments. 1 But the 

 oxygen is gradually taken up by the surplus of oxide, without 

 uniting in any notable proportion with the hydrogen, as has 

 been shown. 



6. The reaction between hydrogen and nitric oxide takes 

 place, howeyer, when it is excited by a series of sparks, but 

 gradually and locally. In fact, at the end of ten minutes the 

 mixture of nitric oxide and hydrogen in equal volumes, NO + 

 H 2 , was reduced to one half in these conditions. After some 

 hours the nitric oxide had disappeared, but there remained 

 several hundredth parts of free hydrogen, and a basic salt had 

 been formed at the expense of the mercury. This latter forma- 

 tion proves that the oxygen set free by the sparks was seized, to 

 a fractional extent, by the nitric oxide to produce nitric per- 

 oxide, a gas, the presence of which was quite manifest. This 

 nitric peroxide gas, in its turn, is partially destroyed by the 

 hydrogen under the influence of the spark, whilst another 

 portion oxidises the mercury, and thus a portion of the oxygen 

 is withdrawn from the ulterior reaction of the hydrogen. 



In a word, the formation of nitric peroxide is intermediate 

 between the decomposition of the nitric oxide and the oxidation 

 of at least a portion of the hydrogen. We have then, 



(1) NO = N + 0. 



(2) NO + = N0 2 . 



(3) N0 2 + 2H 2 = 2H 2 + N. 



Therefore, in order that the hydrogen may be regularly 

 oxidised, it is not the nitric oxide which it is necessary to 

 decompose, but the nitric peroxide, a very stable compound, the 

 destruction of which requires an extremely high temperature. 

 This accounts for the fact that the combustion induced by flame 

 or electric sparks is not propagated. 



7. The same experiments were repeated with a mixture of 

 nitric oxide and carbonic oxide : 



NO + CO. 



According to "W. Henry, this mixture is also not ignited by a 

 lighted match, which is extinguished in it, nor by electric 

 sparks. 



Nevertheless, it was observed that a series of sparks continued 

 during some hours decomposed it completely. Only half of the 

 carbonic oxide is thus converted into carbonic acid, and the 

 combustion is so imperfect that a little carbon is precipitated on 

 the platinum wires, as if pure carbonic oxide had been employed. 

 The surplus oxygen of the oxide forms first of all nitric per- 

 oxide, and then basic salts of mercury. 



Here again, the temperature produced by the spark was 

 1 " Annales de Chimie et de Physique," 5* G^rie, torn. vii. p. 197. 



