62 



BACTERIOLOGY. 



STERILIZATION BY HOT AIR. 



The hot-air sterilizers used in laboratories are simply 

 double-walled boxes of Russian or Swedish iron (Fig. 

 11), having a double- walled door, which closes tightly, 

 and a heavy copper bottom. They are arranged with 

 ventilating openings for the escape of the contained air 

 and the entrance of the heated air. The flame, usually 

 from a rose burner (Fig. 12), is applied directly to the 

 bottom. The heat circulates from the lower surface 

 around about the apparatus through the space between 

 its walls. 



FIG. 11. 



PIG. 12. 



The construction of the copper bottom of the appa- 

 ratus upon which the flame impinges is designed to 

 prevent the direct action of the flame upon the sheet- 



