CH. vii] Nitrolim 137 



proved of value in the Aberdeen experiments. Several 

 crystalline modifications exist, however, one of which 

 is sufficiently non-dehquescent to be of practical value 

 as a fertiliser. This can be stored and drilled and it 

 gave good crop increases at Rothamsted^. 



Calcium cyanamide or Nitrolim'^ 



This fertiliser, like calcium nitrate, is made from air 

 and limestone. There are two stages in the manufacture : 

 first a mixture of calcium carbonate and carbon is heated 

 in an electric furnace to a high temperature, when cal- 

 cium carbide (CaCg) is formed; this is then heated in a 

 stream of nitrogen and gives calcium cyanamide 

 (CaCNa). It was first made at Piano d'Orte in Italy, 

 but now it is produced at Odda in Norway, Alby in 

 Sweden, at Niagara and elsewhere where great supplies 

 of water-power are available. A great increase in supply 

 is anticipated after the war. Calcium cyanamide is not 

 soluble in water and is not a direct plant nutrient. But 

 it decomposes in the soil with formation of calcium 

 carbonate and ammonia, which is then utilised in the 

 usual way. In consequence of the need for this pre- 

 liminary change calcium cyanamide is somewhat slower 

 in action at Rothamsted than sulphate of ammonia. 

 Being insoluble it is not at all likely to be washed out 

 from the soil, while the calcium carbonate formed on 

 decomposition is distinctly valuable. It is best applied 

 at or before the time of sowing so that decomposition 

 may proceed before the plant has grown ; when used as 



1 Joiirn. Bd. Agrir. 1919, xxv. 13.32. 



^ "Kalkstickstoff," in the German papers. There was another sub- 

 stance, not dissimilar, known as "Stickstoti'kalk," which, however, had 

 only a small local sale. 



