138 Fertilisers [pt. hi 



a top dressing some samples have produced harmful 

 effects, but these do not invariably set in. 



Special precautions are taken at the factory to de- 

 compose all the calcium carbide, and in the end the 

 cyanamide is sent out in very finely divided condition. 

 In this state it has proved objectionable to the labourers ; 

 during application to the land it gets into their eyes, 

 inouths and noses, and is the cause of some trouble. 

 Attem ts were made to overcome this by granulation 

 but they led to another difficulty. In presence of an 

 alkali cyanamide polymerises, two molecules joining 

 together to form one of dicyanodiamide, a substance 

 which in any large quantity is poisonous to plants and 

 also to the nitrifying bacteria, and in any case has 

 nothing like the fertilising value of cyanamide. 



Pure calcium cyanamide contains 35 per cent, of 

 nitrogen, but the commercial product contains little 

 more than half its weight of the pure substance, the rest 

 cons sting largely of lime and some graphite. The com- 

 mercial product has therefore received a special name, 

 Nitrolim ; it contains usually 18-20 per cent, of nitrogen, 

 nearly the same as is present in sulphate of ammonia. 



Comparison of these nitrogenous fertilisers 



Table V gives the results obtained at Rothamsted in 

 comparative experiments with these various fertilisers. 



At Cockle Park also nitrolim proved somewhat in- 

 ferior, but there was little to choose between nitrate of 

 soda and nitrate of lime^. 



In 15 experiments at Aberdeen^ the nitrolim proved 



Cockle Park Bull. No. 18, 1912. 



* Aberdeen and North "of Scotland College, Bulletin No. 13, 1909. 

 Trans. Highland and Agric. Society, 1909, 122-134. Journ. Soc. Cheni. 

 Ind. 1918, p. 146. 



