388 NO yes: nitrogen problem in relation to war 



water, three molecules of it forming two molecules of nitric acid 

 and regenerating one of NO. The first reaction has again to 

 produce more NO2 before the next step can take place, and the 

 fact that these reactions must go on successively explains the 

 great difficulty in absorbing these nitric vapors in the absorption 

 towers. Towers 60 feet high and 16 feet in diameter, placed six 

 or eight in a series, are necessary in order to get 88 to 90 per cent 

 absorption of the nitric vapors. As it does not pay to get the 

 last 10 per cent in this way, this portion is absorbed either in 

 caustic alkali, lime, or soda. 



Two of the forms of furnace used may be briefly described. 

 The essence of them all is to form an arc which will have a very 

 large surface so that the gas will be brought into contact with the 

 high temperature and will then cool off very rapidly. Various 

 devices have been used for spreading the arc. The Birkeland- 

 Eyde process, which is the one most used in Norway, uses an 

 electro-magnet. If a magnet is placed at right angles to the 

 arc, the well-known deflection of the electrified particles or 

 electrons passing from one electrode to the other is produced, 

 and thus the arc is drawn out into a disk-shaped flame. Another 

 process for spreading the arc is known as the 'Tauling process," 

 an Austrian process, for which a small installation has been 

 erected in this country at Nitrolee, South Carolina. The elec- 

 trodes are water-cooled metal pipes. The arc forms between 

 them and a blast of air spreads out the arc into the wider portion 

 between the electrodes. 



The arc process, when carried out in the manner described, 

 consumes a very large quantity of electric power, and it is inter- 

 esting to know where that power goes, because in this direction 

 lies the main possibility of substantially improving the process. 

 Of the electric power that is put into the arc only very little 

 (3 or 4 per cent) is consumed in causing the union of nitrogen and 

 oxygen to form nitric oxide. The rest of it is used merely for 

 heating the entering gases from a comparatively low temperature 

 up to the temperature of the arc. Only by devising an adequate 

 preheating system, by which the outgoing gases heat to a fairly 

 high temperature the incoming air, can we hope to increase very 

 greatly the efficiency of the arc process. 



