THK NITROGKX PROBLEM. 101 



reactions take place — e.g., the decomposition of the iiitrons 

 acid yieldini^" nitric oxide, 



3 HNO, > HNO3 + 2 XO + H3O. 



The NO thus produced must be reoxidised by nitric peroxide 

 or oxygen or lost. If reoxidised it is possible that a mixture 

 of nitric oxide and peroxide acting- as jSTjOg may be produced, 

 which is caught by the alkali wash of the last tower yielding 

 sodium nitrite — in fact, the salt obtained from this tower is a 

 mixture of the nitrite and nitrate, in which the former 

 predominates. 



These arc processes depend commercially on a cheap and 

 abundant supply of electric energy, since only 3 to 4 per cent, 

 of the electric energy is used in effecting' the union of the 

 nitrogen M-ith the oxygen ; also, owing to the low concentra- 

 tion of XO, the oxidation and absorption systems must be 

 large and therefore costly. The total cost of electrical energy 

 per kilowatt year at Svaelgfos and Notodden is the smallest in 

 the world, being about tliirteen to fourteen shillings, as com- 

 pared with i)Ounds in this country. 



II.— The Haher Process (1910-13). 



The reaction of nitrogen with hydrogen to form ammonia 

 gas has been known for a long time, as also the fact that the 

 amount of ammonia thus formed is very small. Xernst and 

 Jost in 1907 examined this reaction, using a pressure of 

 50 atmospheres, and at a temperature of 700° C, with 

 manganese as a catalyst, obtained a concentration of less than 

 1 per cent. Haber and le Rossiguol a little later studied the 

 reaction at higher pressures, and with osmium as catalyst 

 obtained an 8 per cent, concentration. The l^adische Anilin 

 and Soda Fabrik then took up the process, and made it a com- 

 mercial success, at the same time undertaking researches to 

 discover cheaper catalytic reagents. The nitrogen is obtained 

 by the fractional distillation of liquid air, and the hydrogen 

 by that of liquid water gas, freed from carbon dioxide before 

 liquefaction. Very little has been published regarding this 

 process other than the scientific researches of Haber and 

 le Rossignol, which showed that the most favourable working- 

 conditions were a pressure of between 100 to 200 atmospheres 

 and a temperature of about 500° C. This gives on the large 

 scale a 5 to 6 per cent, concentration for one passage of the 

 g'ases. From a chemical engineeiring point of view, such 

 conditions were abnormally severe, more especially when 

 dealing' with a gas such as hydrogen. Tliat they have, how- 

 ever, been successfully overcome is now a matter of common 

 knowledge. 



On leaving' tJie furnace where the conversion takes place, 

 the mixed nitrogen, hydrogen a ad ammonia are passed into a 

 refrigerating oi- al>sorption system, wliere the ammonia is 

 liquefied or absorbed, the residual gases being returned to 

 the system. The catalyst in commercial use is believed to be 

 a specially prepared form of iron containing a minute quantity 

 of potash. It is very easilj^ poisoned, and must therefore be 



