NITROGEN FIXATION LOF 221 



brought up to the final process pressure of 100 to 200 atmospheres 

 and washed with chemical solutions for removing the final traces 

 of CO and C0 2 , after which it is passed through the catalytic am- 

 monia reaction chamber. In the Sheffield plant the gas mixture is 

 brought up to its final pressure of 100 atmospheres in one step, and 

 the water scrubbing for removing the carbon dioxide is done at 

 this pressure. 



The gases which have been converted to ammonia in the catalytic 

 chamber are removed by means of refrigeration or water absorption 

 and the uncombined gases returned to the system to be passed 

 through the catalyzer chamber again until finally combined. The 

 ammonia may be sold as anhydrous or aqua, or absorbed in sulphuric 

 acid or phosphoric acid to produce ammonium sulphate or ammo- 

 nium phosphate, the same as with the other processes, or a portion 

 may be oxidized and absorbed to form nitric acid, in which the re- 

 maining portion of the ammonia may be absorbed to form am- 

 monium nitrate. 



In producing hydrogen for synthetic ammonia by the water-gas 

 method, it has been shown how large quantities of carbon dioxide 

 have to be eliminated in the purification. As in the Solvay soda 

 process thousands of tons of carbon dioxide are used each year for 

 which large quantities of limestone are burned, it follows at once 

 that the two processes can advantageously be worked together. 



The ammonia gas and the carbon dioxide are passed into a brine 

 solution, and the products obtained are sodium bicarbonate and am- 

 monium chloride, NaCl+H 2 0+C0 2 +NH 3 =NaHC0 3 +NH 4 Cl. The 

 sodium bicarbonate, NaHC0 3 , is readily converted into soda ash, 

 Na 2 C0 3 , by heating when it loses all its water and part of its carbon 

 dioxide gas, 2NaHC0 3 =Na 2 C0 3 +C0 2 +H 2 0- Soda ash or sodium 

 carbonate is extensively used in the glass, soap, paper, textile, and 

 numerous other industries. 



The ammonium chloride, NH 4 C1, after proper concentration and 

 drying, is at once ready for the market. It is claimed, but not sub- 

 stantiated, that ammonium chloride, which is a more concentrated 

 nitrogen product than the sulphate and meets the other require- 

 ments also, is equal to the sulphate in fertilizer properties, just as 

 potassium chloride is as available for crops as potassium sulphate. 



The power requirements for the Haber process are very low unless 

 the hydrogen should be produced by electrolysis and the nitrogen 

 by liquid-air distillation. The reason for this is, of course, the fact 

 that electricity does not enter into any of the reactions but is chiefly 

 used for motive power. 



Where the nitrogen and hydrogen are provided by the gas producer 

 method the power requirements will amount to about one-half horse- 



1454—25 16 



