ELEMENTARY BACTERIOLOGY LABORATORY EXERCISES 17 
SECTION 6: METHODS OF STERILIZATION 
EXERCISE 25 
PREPARATION OF MATERIALS FOR STERILIZATION 
Prepare Petri dishes, pipettes, empty flasks and test tubes, and test tubes con- 
taining broth, for sterilization, Note carefully the details of the methods used in 
the preparation of glassware for sterilization. 
EXERCISE 26 
METHODS OF STERILIZATION 
For methods of sterilization see “Bacteriology”, Buchanan, pages 105-110. 
Note the various methods of sterilization other than those used in Exercises 27, 
28, and 29. 
EXERCISE 27 
STERILIZATION BY DRY AIR 
Sterilize the pipettes and Petri dishes prepared in Exercise 25 in the hot-air 
sterilizer. Use a temperature of 170° C. Hold for one hour after this tempera- 
ture is reached. 
Is dry or moist heat more efficient as a sterilizing agent? Why? In this con- 
nection also read in “Bacteriology” by Buchanan, pages 172-174. 
EXERCISE 28 
STERILIZATION BY STEAM UNDER PRESSURE 
Sterilize some of the tubes of broth, prepared in Exercise 25, in the auto- 
clave. Use a pressure of 15 pounds for 30 mmutes. Steam under a pressure of 
15 pounds has a temperature of about 121° C. Note carefully the steps and pre- 
cautions to be taken in the operation of the autoclave. 
The time necessary for complete sterilization in the autoclave will vary some- 
what according to the nature of the material, and the amount of material in the 
container. 
