44 



Nitrate of Lime. 



[APRIL, 



industry with a view to the maximum production of various 

 nitrogenous compounds. The output is now mainly available 

 for fertilising purposes, principally in the form of nitrate of lime. 



The process involved in the production of nitrates from the 

 nitrogen of the air consists in passing air through an arc flame 

 (at a temperature of about 3,200 °C.) produced between elec- 

 trodes in a powerful magnetic held. The resulting nitri . oxide 

 gas is then cooled by suitable means and passed through 

 so-called oxidation chambers, where it is given time for complete 

 oxidation to nitrogen peroxide. Subsequently the nitrogen 

 peroxide gas is passed up absorption towers, where it meets 

 a descending stream of water and is converted into nitric 

 acid. For fertilising purposes the nitric acid is then 

 neutralised with limestone, and the product, after solidifi- 

 cation and granulation, is sold as a manure under the name 

 of nitrate of lime. 



The commercial success of the process is dependent on the 

 availability of cheap electric power, which, in Norway, is 

 ensured by the numerous natural gigantic waterfalls. Full 

 advantage has been taken of these natural resources and 

 the huge total of 300,000 to 350,000 h.p. has now been 

 successfully harnessed. The development of the industry 

 in recent years has been phenomenal. In addition to some 

 minor works there are two huge factories, one at Notodden 

 and the other at Rjukan. The present capacity of the combined 

 works is understood to be equal to an annual output of 186,000 

 tons of nitrate of lime or its equivalent per annum. 



The Properties of Mtrate of Lime.— Nitrate of lime contains 

 13 per cent, of nitrogen, which is equivalent to 15*8 per 

 cent, of ammonia. This nitrogen is also in the form in 

 which plants take up their nitrogen under natural conditions, 

 and it does not require, therefore, to undergo any change 

 in the soil before it becomes available to the crop. In this 

 respect it differs from sulphate of ammonia and still more 

 from calcium cyanamide, the nitrogen in which must be 

 transformed into nitrate in the soil before it can be absorbed 

 by plants. In its general nature and use, therefore, nitrate 

 of lime is closely allied to nitrate of soda. 



A further important feature of nitrate of lime from the 

 fertilising point of view is that the nitrate is combined with 

 lime. While a part of this lime may be used for the nutriment 

 of the crop, probably the greater proportion is left behind 

 as carbonate of lime to improve or keep correct the physical 

 and the chemical condition of the soil. 



