54: Laboratory bacteriology. 



EXEKCISE XLII. 

 anaerobic nitrogen fixation. 



1. Measure off eight 100 ce. portions of Winogradsla'a 

 solution in 500 cc. flasks. 



2. To four of these add 10 mgs. (NHJ^SO^. 



3. Plug and sterilize as usual. 



4. Inoculate with 10 cc. (= 5 gms. soil) of 5-minute soil 

 infusions. 



5. Arrange thus: 



1 & 2 — Infusion Soil 1. 



3 & 4— Infusion Soil 1 + 10 mgs. {Nnt)SOt. 



5 & 6— Infusion Soil 2. 



7 & 8— Infusion Soil 2 + 10 mgs. (NH,)jSO,. 



6. Incubate 10-1-1 days in a Novy jar or some other appa- 

 ratus suitable for maintaining anaerobic conditions. 



7. Eemove and digest by the regular Kjeldahl method for 

 total nitrogen. 



