NITROGEN MONOXIDE. 191 



a red heat, or by the electric spark, into nitrogen and oxygen. 

 This decomposition is the easier, as it liberates heat. 



N 2 = N 2 + + 10-3 Cal. 



In this way, it is not accompanied by dissociation, and is not, 

 therefore, reversible. 



Experiments were made with a view of determining at about 

 what temperature this decomposition commences, and if nitric 

 oxide were produced. The monoxide resists the action of a 

 moderate heat better than is generally supposed. By heating 

 it to a dull red, about 520, for half an hour, in a tube of 

 Bohemian glass hermetically sealed, hardly 1-5 per cent, is 

 decomposed into nitrogen and oxygen. The decomposition is, 

 therefore, extremely slow. Let us note here that the trans- 

 formation of nitrogen monoxide into nitric oxide at the ordinary 

 temperature, 



N 2 = N + NO, would absorb - I'O Cal. 



The sudden compression of nitrogen monoxide in an apparatus 

 analogous to the gas tinder box (briquet a gaz) and under con- 

 ditions capable of causing the explosion of a mixture of 

 hydrogen and oxygen only produces traces of decomposition. 



Nitrogen monoxide, mixed with oxygen and brought to a dull 

 red heat in a sealed tube, does not yield nitric oxide, which is 

 intelligible, its formation absorbing heat : i(N 2 -f- = 2NO) 

 would absorb 11 '3. Finally, it must be remembered that 

 nitrogen monoxide does not exert an oxidising action in the 

 cold upon any known body, and that it is neither absorbed nor 

 decomposed by alcoholic or aqueous potash. 



The action of the electric spark on nitrogen monoxide was 

 examined principally in order to study its first phases, for the 

 general products have already been noted by Priestley, Grove, 

 Andrews and Tait, as well as by Buff and Hoffmann. The 

 experiment was made in a sealed tube in order to avoid any 

 secondary action, from water or mercury. 



Decomposition takes place rapidly, and nitrous vapour is 

 immediately formed. One-third of the gas was decomposed 

 within a minute. The decomposed part was divided in nearly 

 equal proportions between the two following reactions : 



N 2 = N 2 +0. 

 4N 2 = N 2 4 + 6JST. 



The first action may be regarded as especially due to the 

 action of the heat of the spark; the second to the heat and 

 electricity combined. Further, both reactions are exothermal : 

 the first liberating + 10'3 Cal., and the second -f 38 Cal., that 

 is to say + 9*5 Cal. for every equivalent of nitrogen monoxide 

 decomposed. At the end of three minutes, with stronger sparks 

 (six Bunsen elements), nearly three-quarters of the gas was 



