DISCOVERY 



123 



there is no question that it would serve as a source 

 of nitrogen for all crops. Unfortunately the process 

 requires considerable electric power. 



A second method gives cyanamide. In this case 

 calciuna carbide is first formed by heating lime and 

 carbon in an electric furnace ; the carbide is then 

 further heated in an atmosphere of nitrogen, when 

 calcium cyanamide is formed. This is not itself a 

 fertiliser, but it rapidly breaks down in the soil to 

 give urea, which further decomposes to ammonia. 

 This process requires less power than the other, but 

 unfortunately cyanamide has disadvantages as manure : 

 it is dusty and unpleasant in use ; is apt to contain a 

 substance toxic to plants, and does not invariably give 



seasons there is little, if anything, to choose between 

 them ; in drier conditions the cliloride is somewhat 

 less effective than the sulphate. The chlorine ion bears 

 possibilities of harmful influence on plants ; when its 

 concentration exceeds a certain value, both the yield 

 and the quality of the crop suffer. These technical 

 difficulties, however, are not insuperable, and the 

 catalytic process remains as an effective contributor 

 to the supply of nitrogen fertilisers. 



Prior to the war the consumption of nitrogen fer- 

 tilisers had doubled in ten years and the output had 

 practically kept pace: since the war there has been 

 serious dislocation in agriculture involving reduced 

 consumption, but the productive capacity had more 



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■fc 



■.'Jixft.^ . 



Showing plots on which fertilisers are tested. 



the increased crop expected. In Central Europe 

 (Switzerland, Germany, etc.) there are large cyanamide 

 plants put up for the purposes of the war, but which 

 could not without serious financial disturbance be 

 scrapped ; ver}' vigorous attempts are therefore being 

 made to overcome the disadvantages of this material. 

 It is too early to say what results may be attained. 

 It has been proposed to convert the cyanamide into 

 urea or into ammonium salts, which could be sold alone 

 or in admixture or combination with phosphates. 



A third method gives ammonia direct by a catalytic 

 process, and from the fertiliser point of view the 

 cheapest product would be ammonium chloride. Ex- 

 periments are in hand at Rothamsted to determine the 

 fertiliser value of this salt as compared with the well- 

 known ammonium sulphate. In wet districts and wet 



than doubled in less than the ten-year period, 

 estimates of the world's production capacity 

 igi2, and 1920 are : 



Output. 

 Long Tons. 



Reliable 

 in 1903, 



1920. 



Productive 



Capacity. 



Long Tons. 



Chile nitrate 

 By-product sulphate 

 of ammonia 

 Fixation industry : 

 Cyanamide 

 Arc process 

 Catalytic process 



1,429,150 2,586,975 2,966,061 



540,200 



Nil 

 Nil 

 Nil 



1,229.773 



126.538 



75,000 



Nil 



2,015,440 



1,777,000 



254.300 

 1,503,000 



1.969.350 4,018,286 8,515,801 



Although many technical problems remain to be 

 solved, it does not appear that any anxiety need be 



