174 



Nature-Study Agriculture 



A fertilizer 

 made from 

 ammonia 



to twelve feet in thickness. It is dug up and purified by 

 separating from it the common salt that is found with 

 it. It is then shipped from Valparaiso to many parts 

 of the world. About three fourths of it is used for 

 fertilizer, and much of the rest is used for making ex- 

 plosives. 



Household ammonia contains nitrogen and is often 

 put into water that is used on house plants. But as 

 it evaporates so readily, ammonia is not suitable for use 

 as a field fertilizer. It is easily changed, however, to a 

 solid compound called " sulfate of ammonia." This is 

 done by adding sulfuric acid to the ammonia and evapo- 

 rating the mixture. (Exp. 3.) The dry, solid sulfate 

 of ammonia, looking like salt, is left. This is a very 

 valuable fertilizer. It contains more nitrogen than any 



Illustrated World 



FIG. 135. Sulfate of ammonia, an important nitrogen fertilizer, made as a 

 by-product in the manufacture of coal gas and coke. 



