88 MANUFACTURE OF FERTILIZING MATERIALS ' 



century, Raymond Lulle called this body sal- 

 nitri. Since then the term saltpetre has been used 

 to designate nitrate of potash, while nitrate of 

 soda is called Chili saltpetre, cr nitre. 



Nitric acid consists of nitrogen, oxygen, and 

 hydrogen; its chemical formula is HN0 3 . It 

 thus contains fourteen parts of nitrogen (22.2 

 per cent), forty-eight parts of oxygen (76.19 

 per cent), and one part of hydrogen (1.59 per 

 cent.) It forms a very caustic fuming liquid. 

 In the concentrated state it has a density of 1.52, 

 but the commercial acid is generally much weaker 

 It decomposes easily. It gives up a portion of 

 its oxygen to oxidizable bodies, such as carbon, 

 sulphur, sulphurous acid, and then passes to less 

 highly oxidized states. Metallic zinc reduces 

 dilute nitric acid, and converts it into nitrate 

 of ammonia. With bases it forms salts, which 

 with the exception of some basic metallic salts, 

 are soluble in water. Nitric acid is formed al- 

 most exclusively by the oxidation of ammonia, 

 or of nitrogenous matter of animal origin, under 

 the action of the air in presence of bases such 

 as the carbonate of lime. However, this spon- 

 taneous formation in the soil is very slow. It 

 is, on the other hand, very rapid in Southern 

 countries, where the conditions of temperature 

 and of moisture in the air conduce considerably 

 to the oxidation of nitrogenous animal matter. 



South American nitrate of soda is distinguished, 

 more especially frpn^ ^ordinary saltpetre, by the 



