CHEMICAL PROPERTIES 15 



horn and hoof also with 15 per cent of nitrogen. Chincha 

 guano in its best days seldom reached 14 per cent of nitrogen. 

 The highly concentrated character of sulphate of ammonia 

 renders it especially suitable for conveyance over long dis- 

 tances ; as much nitrogen can be conveyed in 10 tons of 

 sulphate of ammonia as in 13 tons of nitrate of soda. This 

 same concentrated character also makes the salt a great 

 favourite with the manufacturers of mixed manures, as a higher 

 percentage of nitrogen can be given to the manure by the in- 

 troduction of sulphate of ammonia than by any other means. 



The sulphate of ammonia, like many other salts of am- 

 monia, is completely volatilised by heat ; at a low red heat it 

 rises in vapour and disappears in the air. This fact is of great 

 use in detecting adulteration. If a sample of the salt leaves a 

 distinct residue when maintained at a low red heat till vapour 

 ceases to be produced, it certainly contains something besides 

 sulphate of ammonia. 



Sulphate of ammonia is not a hygroscopic salt ; that is, 

 it does not become sensibly damp by exposure to moist air. 

 This property is a great help to its convenient use, and saves 

 the farmer much trouble. It also enables the manure manu- 

 facturer to employ the salt freely in the preparation of mixed 

 manures, without danger of these losing their powdery con- 

 dition by storing. Any mixture of nitrate of soda with sul- 

 phate of ammonia is to be avoided, as the mixture becomes 

 deliquescent in moist air, and easily suffers decomposition ; 

 these results are due to the formation of nitrate of ammonia. 



Sulphate of ammonia is a very soluble salt, dissolving in 

 about twice its weight of cold water. This easy solubility in 

 water greatly aids its rapid distribution in the soil. It is 

 often stated in popular writings that sulphate of ammonia is 

 less soluble than nitrate of soda, and that it is the greater 

 solubility of the nitrate which occasions its more rapid washing 

 out of the soil in wet weather. This statement is entirely 

 erroneous. When sulphate of ammonia is applied to a moist 

 soil it will very speedily be brought into solution. That a 

 fertile soil is capable of retaining ammonia in spite of the 

 washing effect of rain is quite true ; but as we shall presently 



