HYDROGEN AND NITRIC OXIDE. 61 



ment was repeated, doubling the quantity of oxygen, so that the 

 proportion of this element sufficed for the combustion of the 

 hydrogen and also nitric oxide. 



The reaction produced under these conditions does not give 

 rise to the combustion of hydrogen, the nitric peroxide being 

 formed alone, whether the nitric oxide be introduced into the 

 mixture made beforehand of oxygen and hydrogen, or the oxygen 

 be introduced into a mixture previously formed of hydrogen and 

 nitric oxide. 



Now the temperature developed by this formation would be 

 927, according to the calculation based on the known specific 

 heats of the elements, and supposing that of the nitric peroxide 

 to be equal to the sum of its components. It seems difficult to 

 explain these facts, except by supposing the real temperature to 

 be much lower ; that is, by attributing to the nitric peroxide 

 a specific heat greater than that of the elements, as is the case 

 with the chlorides of phosphorus, arsenic, silicon, tin, titanium, 

 etc., in the gaseous state, 1 and probably increasing with the 

 temperature, as in the case of carbonic acid. 



This has, in fact, been verified experimentally by the author 

 and M. Ogier. 2 The temperature, calculated according to these 

 new data, falls to 700, and even lower. 



There is, moreover, no exceptional property of the nitric 

 oxide to prevent combustion. In fact, if the inflammable 

 temperature of a mixture of oxygen and combustible gas, such as 

 oxygen and phosphoretted hydrogen, be notably lower, it will 

 suffice to introduce a few bubbles of nitric oxide, in order to 

 ignite it at once. 



4. When these experiments, with a mixture of hydrogen and 

 nitric oxide, are carried out over mercury, a complication takes 

 place which corresponds to a new distribution of the oxygen, 

 the mercury intervening as a third combustible body, forming 

 basic nitrates and nitrites. 



The quantity of oxygen absorbed is almost double, but the 

 hydrogen remains unconsumed. 



5. These facts being admitted, let us see what happens when 

 we try to ignite a mixture of hydrogen and nitric oxide. 

 Berthollet and H. Davy found that ignition does not take 

 place, either under the influence of the electric spark, or the 

 influence of a body in a state of combustion. Further, a lighted 

 match is extinguished in a similar gaseous mixture. If some- 

 times the hydrogen of this mixture becomes ignited, it is outside 

 the test tube and at the expense of the oxygen in the atmo- 

 sphere. 



Nevertheless, the flame of the match, or the electric spark, 

 brings about, at the point heated, decomposition of nitric oxide 



1 " Essai de Me'canique Chimique," torn. 1. pp. 336 and 400. 



2 " Bulletin de la Socie'td Chimique," 2' s^rie, torn, xxxvii. p. 335. 



