NITEOGENOUS MANUBES 271 



whole of the previous year. Numerous other companies 

 have since been formed to exploit the manufacture. 



NITROLIM (CALCIUM-CYANAMIDE). 



Calcium carbide, which is now extensively used for 

 the preparation of acetylene gas, is manufactured on a 

 large scale by heating lime and carbon together in an 

 electric resistance furnace. If nitrogen be introduced at 

 a very high temperature, it also enters into combination, 

 and a compound called calcium cyanamide is formed. 



According to the formula, CaCN 2 , ascribed to it, the 

 pure substance contains 35 per cent, of nitrogen, which 

 is equal to 42*5 per cent, of ammonia. Until a few 

 years ago all substances of this class were supposed to 

 be poisonous to vegetation, and quite unsuitable for 

 mammal purposes. It has been found, however, that 

 calcium-cyanamide in aqueous solution is slowly hydro- 

 lysed ; the calcium is separated as calcium hydrate, and 

 the nitrogen is converted into urea, ammonia and other 

 similar products, which are quite innoxious. In the soil 

 this change takes place more rapidly, and appears to be 

 facilitated by the presence of organic matter. The 

 changes also proceed further ; the calcium hydrate is 

 converted into the carbonate; amide bodies, e.g., urea, 

 are completely hydrolysed to ammonium carbonate, which 

 undergoes nitrification, and the nitrogen is thus ulti- 

 mately converted into nitrates. The presence of calcium 

 in the form in which it exists in the compound, thus 

 imparts a certain basic character to it. This has a 

 beneficial effect on the properties of the soil generally, 

 and is particularly useful in promoting the nitrification of 

 the ammonium compounds produced by the hydrolytic 

 changes. Assuming that calcium carbonate and ammon- 

 ium carbonate are the natural end of the first stage, the 



