NITROGENOUS MANURES. 127 

 NITROGENOUS MANURES. 



1. Sulphate of ammonia. This is obtained, 

 as a by-product in the manufacture of gas from 

 coal, in the form of small, white or grey crys- 

 tals. When heated with lime, or other alkali, 

 it gives off' ammonia gas which is easily 

 recognised by its pungent smell. Sulphate of 

 ammonia contains about 20 per cent, of nitro- 

 gen (equal to about 24 per cent, of ammonia) 

 It is a quick acting manure, although not nearly 

 so rapid as nitrate of soda, and can be applied 

 in comparatively large doses without risk of 

 loss. It gives excellent results on clayey lands. 



2. Nitrate of soda or Chili saltpetre. This 

 is obtained from certain deposits in Chili. It 

 occurs in commerce in larger crystals than 

 sulphate of ammonia and has a tendency to be- 

 come damp by the absorption of moisture from 

 the air. For this reason it should be stored in 

 a perfectly dry place. It may be recognized by 

 placing a fragment on a piece of burning char- 

 coal, when it flares up and burns. Nitrate 

 of soda contains upwards of 16 per cent, of 

 nitrogen. It is very rapid in its action ; the 

 plant being able to use it at once. It is readi- 

 ly washed out of the soil and should never be 

 applied in large doses. 



3. Dried blood occurs in the form of dark 



