6 LABORATORY BACTERIOLOGY 



The projecting part should be about the same length and be 

 of equal firmness. (For method of closing the tubes more 

 securely, see paragraph 22.) 



9. Sterilizing Glassware. — Place all the tubes, flasks, 

 and Petri dishes in the hot-air sterilizer, close the door tightly, 

 and light the gas. Heat the air in the sterilizer to a tempera^ 

 ture of from 135 to 150° C. and keep it there for one hour. 

 The temperature should not be allowed to go above 150° C. 

 Turn the gas off, and when the temperature of the air in the 

 sterilizer goes down to or below 45° C. the door may be opened 

 and the apparatus removed. 



