DENITEIFICATION IN SOLUTION. 35 



GROUP III. DENITRIFICATION. 

 Exercises XXV. to XXIX. 



EXBKCISE XXV. 



DENITEIFICATION IN SOLUTION. 



1. Place 10 cc. of the "Giltay" solution in each of six test 

 tubes. 



2. Plug and sterilize in the autoclave. 



3. Arrange thus : 



1 & 2 — nothing. 



3 & 4^0.1 gm. soil. 



5 & 6 — 0.1 gm. horse manure. 



4. Incubate 7-8 days at 20° C. 



5. Test qualitatively for nitrates, using a diphenylamine 

 solution in sulphuric acid — a blue coloration indicates the 

 presence of nitrates. 



