NO yes: nitrogen problem in relation to war 387 



this reaction into a technical process. However, a German 

 chemist, Haber, demonstrated, by working at high pressures and 

 at the same time at the low temperatures made possible by the 

 discovery of a good catalyst, that this reaction can be carried 

 out on a commercial scale, and this is in fact being done very 

 extensively in Germany. 



4. Finally, we have the arc process, which, like the synthetic 

 process, involves an extremely simple chemical reaction : 



■ N2 + Oo = 2N0. 



At a very high temperature nitrogen and oxygen unite to form 

 nitric oxide. In this case the effect of temperature on the equi- 

 librium is exactly the opposite of its effect on the ammonia equi- 

 librium. The higher the temperature, the more nitric oxide is 

 obtained; but there is very little until the temperature becomes 

 very high. At 1600°, 0.4 per cent (by volume) of a mixture of 

 equal parts nitrogen and oxygen is converted into nitric oxide; 

 at 1900°, 1.0 per cent; and at 2400°, 2.2 per cent. It is clear, 

 then, that we can get a considerable production of nitric oxide 

 only by operating at a high temperature. But not only is it 

 necessary to operate at a high temperature, but the gases must 

 be cooled so quickly that in the process of cooling the reaction 

 does not go back again. The gas must be cooled rapidly to such 

 a temperature that the rate of decomposition of nitric oxide into 

 oxygen and nitrogen is made very small. The only really 

 practical way in which this can now be carried out is by using an 

 electric arc. An arc produces locally an extremely high tem- 

 perature, and the gas can be drawn rapidly away from the arc 

 and quickly cooled. 



Before describing the ways in which this reaction is carried 

 out commercially, I shall first call attention to the remaining 

 reactions which are involved in the production of nitric acid by 

 the arc process. The nitric oxide, when the gas cools to below 

 150°, combines with oxygen to form nitrogen peroxide: 



2N0 + 02= 2NO2. 



This reaction does not take place instantly and time must be 

 allowed for its completion. The peroxide is then treated with 



