AMMONIFICATION OF UREA. 23 



EXEECISE XVI. 



AMMONIFICATION OF UEEA. 



1. Measure off six 100 gram portions of "urea solution" 

 into 500 cc. flasks. 



2. Plug and sterilize in the autoclave at 10 lbs. pressure 

 for 10 minutes. 



3. Arrange thus : 



1 & 2— nothing. 



3 & 4 — Add 20 cc. (=10 gms. soil) of a 5-minute infusion of 

 a fresh garden soil. 



■ 5 & 6 — Add 20 cc. (=10 gms. soil) of a 5-minute infusion of a 

 pasteurized garden soil (to pasteurize the soil, heat it to 70° C. for 

 30^0 minutes). 



4. Incubate 2-3 days at 20° C. 



5. Pipette off two 10 cc. portions of each culture and 

 titrate the ammonia present with J^ HCl, using cochineal 

 as an indicator. 



6. From the results obtained calculate the total quantity 

 of ammonia produced and the per cent, of urea transformed. 



