NITRATE OF LIME AND NITROLIM 115 



Nitrate of Lime. 



Nitrate of lime is prepared from the atmospheric nitrogen by a 

 modern extension of the original Cavendish process. The product 

 is generally clean and free from extraneous matter, and averages 13 

 per cent, nitrogen. It can be valued on exactly the same basis as 

 nitrate of soda, and its analysis is carried out in a similar manner. 

 Its chief disadvantage is its hygroscopicity ; it absorbs moisture 

 from the atmosphere more readily than any other manure in 

 common use. 



^7. Hygroscopicity of Nitrate of Lime. 



(a) A quantity of the fertiliser on exposure to a 

 moist atmosphere quickly becomes moist, then pasty, 

 and finally liquid. 



{b) Comparative Hygroscopicity. — Into three clock- 

 glasses are weighed equal quantities of nitrate of lime, 

 nitrate of soda, and sulphate of ammonia. The clock- 

 glasses are placed under a large bell-jar, in which is 

 placed a beaker of water to keep the enclosed atmo- 

 sphere of a constant moisture content. The dishes 

 should be weighed every two or three hours, and the 

 increases in weight, showing the amounts of water 

 absorbed, plotted out graphically for comparison. 



Calcium Cyanamide or Nitrolim. 



This material is prepared from atmospheric nitrogen by 

 combination with heated calcium carbide. Chemically it consists 

 essentially of CaCN2, but it also contains excess of lime, about 

 20 per cent, free carbon, and small quantities of calcium carbide — 

 CaCg. In the presence of water, as for example in the soil, the 

 cyanamide gradually decomposes into free ammonia and calcium 



carbonate : 



CaCN2 + 3H20 = 2NH3 + CaC03. 



It consequently acts as a basic manure. Commercial nitrolim 

 contains about 20 per cent, of nitrogen, which is in a fairly readily 

 available condition. Its chief drawbacks are its light powdery 

 condition and its frequent slight content of calcium carbide and 



