20 LABORATORY BACTERIOLOGY. 



EXEECISE XIV. 



THE RELATIVE AirOt'NTS OF AMjMONIA AND CARBON DIOXID 



FORICED IN THE AJIMONIFICATTON OF NITROGENOUS 



MATERIALS. 



1. Weigh off six 100 gram portions of air-dry, sieved soil, 

 in tumblers. 



'i. Add dried blood and cottonseed meal as follows: 



1 & 2— nothing. 



3 & 4 — 5 grams dried blood. 



.5 & 6 — 5 grams cottonseed meal. 



3. Stir tlioroughly. Add optimum proportion of water 

 and 12 cc. additional for the dried blood and cottonseed 

 meal. 



4. Cover tumblers and place them under bell-jars of 1-5 

 liters capacity, standing on ^'aselined ground glass plates. 

 At the same time place under each bell-jar an Erlenmeyer 

 flask containing 10 cc. of a standard barium hydrate solution 

 each cc. of which is equivalent to approximately 3 milli- 

 grams of carbon dioxid. 



5. Bemove and titrate the barium hydrate at the end of 

 each day for six consecutive days, replacing it by fresh por- 

 tions. The air under each bell-jar is renewed at the same 

 time, by lifting it from the plate and turning it up and 

 down several times. Eecord the amount of carbon dioxid 

 produced. 



6. At the end of six days transfer the contents of each 

 tum1)ler into a copper flask, add water and magnesium 

 oxid, distil and titrate. 



