NITROGEN 131 



electric energy, three factories have been established, where, 

 in 1911, there was manufactured calcium nitrate to the 

 value of $350,000. Air at the rate of 25,000 liters per 

 minute is sent through the electric arcs spread by powerful 

 electro magnet. About 1 per cent of the total volume of 

 gas is oxidized to nitric oxide (NO). This oxide leaves the 

 apparatus through a tube kept at a temperature of 500-700 

 Centigrade; the gases are then rapidly cooled to 50-60 

 C., a temperature favorable to the further oxidation of 

 the nitric oxide to nitrogen tetroxide (NO 2 ). This product 

 reacts with water to produce nitric and nitrous acids. 

 The equation expressing this reaction is 



2NO 2 +H 2 O = HNO 3 +HNO 2 . 



The nitric products that fail to be absorbed in the water 

 are caught in a milk of lime trap as calcium nitrate and 

 calcium nitrite. The latter is liberated as nitrous oxide 

 by treating with nitric acid. The reaction is 



Ca(NO 2 ) 2 +2HN0 3 = 2HN0 2 +Ca(NO 3 )2. 



The nitrous oxide is again put through the process of con- 

 version into nitric acid. At least 95 per cent of the oxide 

 of nitrogen formed is transformed into nitric acid of 50 

 per cent strength. The nitric acid is converted into nitrate 

 of lime by adding it to the correct quantity of calcium 

 carbonate, according to the reaction 



2HNO 3 +CaCO 3 = Ca(NO 3 )2+CO 2 +H 2 O. 



The nitrate of lime formed is 75 to 80 per cent pure, and 

 contains about 13 per cent of nitrogen. This material 

 must be shipped in casks on account of its deliquescence. 

 The deliquescence of normal calcium nitrate has led to 

 the manufacture of some basic nitrate of lime, which is 

 accomplished by the addition of the proper amount of 

 quicklime to the hot solution. The equation is 



CaO+Ca(NO 3 ) 2 = Ca 2 O(NO 3 ) 2 . 



