30 LABORATORY BACTEEIOLOGV. 



EXEECISE XIX. 



NITKIFICATION IN SOLUTION. 



1. Measure off four 100 cc. portions of "nitrite solution 

 for nitrification" into 250 cc. Erlenmeyer flaslfs. 



2. Plug and sterilize as usual. 



3. Then inoculate in duplicate with 20 cc. portions 

 (= 10 gms. soil) of 5-ininute infusions %i the two soils to 

 be tested. 



4. Incubate for 4 weeks at 20° C. 



5. At the end of that time, filter and wash thoroughly 

 and determine the nitrates present in some convenient 

 aliquot of the solutions by means of the phenol-sulf onic acid 

 method. 



6. Calculate the per cent, of the original nitrite nitrogen 

 nitrified by the soils. 







.^- 



I 



%- 



