MANURES. 293 



NEW NITROGENOUS MANURES. 



A recent estimate puts the exhaustion of the nitrate beds 

 of South America at some 25 to 30 years from the present. 

 In view of this, and of the fact that the output of a 

 bye-product like sulphate of ammonia must always be 

 necessarily limited, the question of new nitrogenous 

 artificials is becoming of first importance. 



Within the last few years two such manures have been 

 successfully produced and put on the market and are 

 beginning to be known to the agriculturist. 



These are "nitrate of lime" made in Norway, and "lime 

 nitrogen" or "nitrogen lime" an impure form of the 

 compound calcium cyanamide CaCN 2 made in Germany 

 and Italy. Both manures derive their nitrogen from the 

 atmosphere but can only be produced where water power 

 is plentiful, as cheap electricity is essential to their 

 profitable manufacture. 



NITRATE OF LIME. 



In the preparation of this substance a current of air is 

 passed through a specially constructed electric furnace 

 nd a certain amount of combination of the nitrogen and 



o 



oxygen takes place with the formation of the gas nitric 

 oxide NO. This nitric oxide which forms about 1 % 

 of the air leaving the furnace is made to unite with more 

 oxygen and with water forming a mixture of nitrous and 

 nitric acids which by treatment with milk of lime gives 

 a mixture of the calcium salts of these acids. The calcium 

 nitrite in the mixture is converted into nitrate by means 

 of nitric acid (of previous manufacture) and the solution 



