POTASSIUM, SODIUM, ETC. 131 



salts, the material readily absorbs moisture from the air 

 while other compounds cause it to form lumps and hard 

 cakes. Hence a salt which readily absorbs moisture or 

 forms hard lumps is not a pure one. Sodium chlorid 

 takes but little or no part in plant life but is necessary 

 for animal life. 



161. Sodium Nitrate. Extensive deposits of sodium 

 nitrate are found in Peru, Chile, and other South Ameri- 

 can countries. It is commonly called Chile saltpeter. 

 As stated in Section 154, it is extensively used for the 

 preparation of potassium nitrate and in the manufacture 

 of nitric acid and commercial fertilizers. Sodium nitrate 

 is commercially and agriculturally an important product. 

 The value of nitrogen in fertilizers is usually based upon 

 its selling price. Small amounts of this salt formed by 

 the process of nitrification are found in soils of high fer- 

 tility. Because of its solubility, however, sodium nitrate 

 never accumulates in soils. 



162. Sodium Carbonate. Commercially, this salt is 

 known as soda and is one of the most useful chemicals 

 manufactured. It is extensively used in the making of 

 soap and glass, and in other commercial operations. It 

 is prepared by two processes, one known as the Le Blanc 

 process, and the other as the ammonia or Solvay process. 

 By the L,e Blanc process, it is prepared from sodium 

 chlorid treated with sulfuric acid which produces Na 2 SO 4 . 



2NaCl + H 2 SO 4 Na 2 SO 4 + 2HC1. 

 The sodium sulfate is heated with charcoal which pro- 

 duces sodium sulfid. 



Na 2 SO 4 + 2C = Na 2 S + 2CO 2 . 



