BACTERIOLOGICAL TECHNIC 



iron. Some forms have a cover, others a door on one 

 side. A basket, or a set of shelves, is on the inside. 

 A gauge indicates the pressure and temperature. A 

 safety valve opens automatically when the desired 

 pressure is reached. Two 

 forms are illustrated in 

 Figs. 9 and 10. 



Before using the auto- 

 clave the inside should be 

 examined. It must be 

 clean and contain a suffi- 

 cient quantity of clean 

 water. Water containing 

 impurities is liable to foam 

 up when boiling, wet the 

 plugs, and ruin the media. 

 If the lid is on top, it 

 should be fastened care- 

 fully by tightening the 

 thumbscrews. In order 

 to distribute the pressure 

 of the lid uniformly the 

 diametrically opposite 

 screws should be tight- 

 ened simultaneously. The 

 valve should be open and 

 left open until the steam 

 has escaped for about one 

 minute. Then the valve 

 is closed and when the desired pressure has been 

 reached, the gas should be turned down so as to 

 maintain pressure for the requisite length of time. 



e 



FIG. 9 

 Autoclave 



a. Steam valve d, d. Thumbscrews 



b. Safety valve . Bunsen burner 



c. Gauge and opening 



