13'2 Fertilisers [pt. in 



was started by Sir William Crookes in 1 898, and is carried 

 on at Notodden in Norway and at Niagara where abun- 

 dance of cheap water-power occurs, and the process con- 

 sists in burning air in an extremely hot flame probably 

 3000-3500 C. by means of a powerful electric arc in 

 a small chamber : the products are then made to react 

 with lime. 



In ordinary circumstances nitrogen is not combustible 

 and the mixture of nitrogen and oxygen in the air is not 

 inflammable, but at this very high temperature the 

 nitrogen bums and unites with the oxygen to form 

 oxides, chiefly nitric oxide. The gases are cooled, and 

 mixed with air, when a higher oxide, nitrogen peroxide, 

 is formed ; they are then drawn with fans through towers 

 packed with broken quartz down which water trickles, 

 and become converted into a dilute mixture of nitrous 

 and nitric acids and finally into nitric acid. This is then 

 neutralised with limestone and the solution on evapora- 

 tion yields calcium nitrate i. 



The first samples to be placed on the market were not 

 easy to use as they so readily absorbed moisture and 

 became converted into a sticky pasty mass, but this 

 difficulty was overcome prior to the war by making a 

 basic nitrate; the samples then obtainable contained 

 13 per cent, of nitrogen. 



As a fertiliser calcium nitrate closely resembles sodium 

 nitrate, but it appears to be free from the disadvantage of 

 making heavy soils sticky. Further experience is needed 

 before any very definite statements can be made, but so 

 far as present knowledge goes nitrate of lime is a very 

 promising addition to the list of nitrogenous manures. 



' For details of the process of manufacture see paper by Eyde, Journal 

 of the Royal Society of Arts, 1909, vol. Lvii. p. .568. 



