240 



GENERAL MICROBIOLOGY 



2. Place 5 gms. of the soil in one of the flasks and mix 

 it with 50 c.c. of water. 



3. Arrange the 100 c.c. graduate in a water bath for 

 collecting gas, by filling with water and inverting mouth 

 down, under water. Clamp it in place. 



4. Then add 20 c.c. of 3% hydrogen peroxide to the flask 

 containing the soil, stopper the flask and, keeping the 

 mixture moving, collect the oxygen in the graduated tube 

 over water. Record the time for maximum oxygen libera- 

 tion. 



5. At the same time determine the part played by bac- 

 teria and enzymes, by repeating the catalase test on soil 

 that has been heated in the autoclav at 15 Ibs. pressure 

 (120 C.). 



6. Also determine the part played by humus by repeat- 

 ing this test with the same earth, having burned the humus 

 by heating with the flame. 



7. Record your results according to the diagram follow- 

 ing: 



8. What part does each factor play in the liberation 

 of oxygen? Is this action in soil of any value? If so, 

 what? 



9. Compare your results with those of the catalase 

 test in milk. By which substance is the most oxygen 

 liberated? Is there a logical explanation for this? 



10. Give all results in full, draw any conclusions that 



