322 



SOILS AND FERTILIZERS 



and absorbed by the water in the second test tube; the reaction 

 is due to the presence of the ammonia. 



Experiment No. 22 

 Testing for Nitrates 



Dissolve about 50 milligrams of sodium or potassium nitrate in 



100 cc. H 2 O. To 15 cc. 

 of this solution add 2 cc. 

 of a dilute and clear solu- 

 tion of FeSO 4 , and place 

 the test tube in a cylinder. 

 Through a long-stemmed 

 funnel add 2 or 3 cc. H 2 SO 4 . 

 Observe the dark brown 

 ring that is formed ; H 2 SO 4 

 liberates HNO 3 as a free 

 acid, which in turn changes 

 the iron from the ferrous 

 to the ferric state ; the dark 

 brown color is due to the 

 nitric acid forming interme- 

 diate compounds during 

 this operation. 



FIG. 59. Testing for Nitrates. 



Experiment No. 23 

 Volatilization of Ammonium Salts 



In separate test tubes place about o.i gm. each of ammonium 

 carbonate and ammonium sulphate. Apply heat gently to each and 

 observe the result. Observe that the ammonium carbonate readily 

 volatilizes and some is deposited on the walls of the test tube while 

 the ammonium sulphate is much less volatile. In poorly ventilated 

 barns, deposits of ammonium carbonate are frequently found. 



