TRANSACTIONS OF WAGNER 



FOOD FROM THE AIR 



stituting one electrode, and an iron pipe extending some distance up the tube, 

 the other electrode. Air at a temperature of about 500° is admitted at con- 

 siderable pressure near the lower electrode and causes the arc to be elon- 

 gated, and also carries the products of oxidation up the tube to a cooling cham- 

 ber, from which they are taken to the absorbing liquid. 



y^^'/j-:'^^>.^T^\Y^ 



Diagram of Birkeland-Eyde furnace. Trans. Far. Soc, 1906, 2, 



rMnmmr—Qr- 



+ 







+ 



Diagram of arc of Birkeland-Eyde furnace. Trans. Far. Soc, 1906, 2, 98. 



The combination of oxygen with nitrogen in these and similar forms of 

 apparatus usually involves careful regulation of the temperature, as the reac- 

 tions are of the type termed "reversible," that is, decomposition into free 

 nitrogen and oxygen will take place almost as rapidly as combination. Nernst 



