452 NATURE AND PROPERTIES OF SOILS 



The product is a black dry crystalline powder of rather 

 light weight, containing about 20 per cent, of NH 3 . It is very 

 impure as shown by the following analysis: 



CaCN 2 45.9 C 13.1 



CaC0 3 4.0 Fe 2 3 and A1.,0 3 1.9 



CaS 1.7 Si0 2 1.6 



Ca a P 2 1 MgO 1 



Ca(0H) 2 26.6 H 2 3 



Its odor and the presence of carbon are characteristic. It 

 is intensively alkaline to litmus. In the soil it undergoes a 

 number of very complex changes, urea ultimately being pro- 

 duced. Toxic compounds are present as the reactions pro- 

 ceed. It should, therefore, be placed in the soil some time be- 

 fore the crop is seeded. The carbon seems to aid in the trans- 

 formation as a catalytic agent. The urea quickly breaks 

 down biologically to ammonia : 



CON 2 H 4 + 2H 2 = (NH 4 ) 2 C0 3 



This ammonia is then oxidized to the nitrate form. 



251. Basic calcium nitrate (Ca(N0 3 ) 2 +).— This fertil- 

 izer, like calcium cyanimid, is produced by the artificial fixa- 

 tion of nitrogen. Air is passed through an electric arc of high 

 temperature. Under such conditions a part of the oxygen and 

 the nitrogen are forced together forming nitric oxide. This 

 gas is then oxidized in suitable chambers to the peroxide, 

 which is passed into water, producing nitric acid. The nitric 

 oxide which also results is led back to the oxidizing chambers. 



The reactions are as follows : 



N 2 + 2 = 2NO 



2NO + 2 = 2N0 2 



3N0 2 + H 2 = 2HN0 3 + NO 



The nitric acid is passed into lime-water, giving calcium 

 nitrate. This fertilizer contains from 13 to 16 per cent, of 

 ammonia and is intensely alkaline to litmus. Due to its high 



