INFLUENCE OF FINENESS. 15 



BXEECISE IX. 



THE INFLUENCE OF FINENESS OF DIVISION OF DRIED BLOOD 

 ON ITS AMMONIFICATION. 



1. Weigh off in tumblers eight 100 gram portions of air- 

 dry, sieved samples of soil. 



2. Arrange thus : 



1 & 2 — 5 grains dried blood, unsieved. 



3 & 4 — 5 grams dried blood through 2 mm. sieve. 



5 & 6 — 5 grams dried blood through 1 mm. sieve. 



7 & 8 — 5 grams dried blood through J mm. sieve. 



3. Stir all very thoroiaghly by means of a sterile spatula. 



4. Prepare a soil infusion of the soil employed by shak- 

 ing 100 grams of a fresh sample in 200 cc. of sterile water 

 for 5 minutes. 



5. By means of sterile pipettes inoculate each of the eight 

 portions of soil with 10 cc. of this infusion. 



6. Add sterile water to bring the moisture content up to 

 the optimum for the soil, using 12 cc. additional for the 

 dried blood. 



7. Cover with Petri dish covers and incubate 7-8 days at 

 20° C. 



8. Then transfer the soil to copper flasks and determine 

 the ammonia present as described in Exercise V. 



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