26 



CHEMICAL FERTILIZERS 



TABLE 4. 

 NITRE-EARTH DRAINAGE LIQUORS. 



Potassium nitrate 

 Potassium chloride 

 Sodium chloride 

 Calcium chloride 

 Magnesium chloride 

 Calcium sulphate 

 Magnesium sulphate 



Per cent. 

 7-24 

 0-4 



15-25 

 O'l 

 0'2 

 0-1 

 O'l 



This liquor is either boiled down in iron or earthen pans by 

 means of heat from burning wood, or is allowed to concen- 

 trate in shallow trays by sun heat. The latter method is 

 chiefly used in the Punjab. As concentration proceeds, 

 sodium chloride is first deposited, especially when the opera- 

 tion is conducted over a fire at a temperature approaching 

 boiling point. In this last case, when the liquors have been 

 sufficiently concentrated, they are allowed to cool, and the 

 s altpetre crystallizes out. The saltpetre so obtained is usually 

 sent to a refinery for the manufacture of gunpowder, but the 

 crude materials are sometimes used for manure. The 

 nitre earths are also used directly for manurial purposes. 

 The finished crude saltpetre varies considerably in composi- 

 tion from 25 % to 75 % : sodium chloride is an invariable 

 impurity, and sodium sulphate is usually present to some 

 considerable extent. Typical analyses are given in Table 5. 



TABLE 5. 

 CRUDE NITRE. 



It is probable that the existing sources of potassium nitrate 

 in India might be further utilized ; artificial nitre beds 

 might be established there. Deposits of nitre, derived from 

 rabbit dung, occur in the Griquatown and Pretoria beds, 

 South Africa. 



