130 NATURE TEACHING 



of small white or grey crystals. 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 nitrogen (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. 



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 become damp by the absorption of moisture 

 from the air. For this reason it should be stored in a 

 perfectly dry place. It may be recognised by placing a 

 fragment on a piece of burning charcoal, 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 readily washed 

 out of the soil, and should never be applied in large 

 doses. 



Dried blood occurs in the form of dark brown grains 

 or powder containing from 10 to 14 per cent, of nitrogen. 

 It also contains small amounts of potash and phosphate. 

 Dried blood, being insoluble, cannot be used at once by 

 the plant, but requires to be altered first. It is therefore 

 lasting in its action. 



Phosphatic Manures. 



Phosphate of lime occurs in nature (as an insoluble 

 substance), in bones and in certain mineral deposits. 



