38 METHODS OF STERILISATION 



out automatically, the manometer being fitted with an 

 adjustable pointer which can be set to any required 

 pressure-temperature and so arranged that when the 

 index of the manometer coincides with the adjustable 

 hand the safety valve is opened. 



7. Extinguish the gas and allow the manometer 

 index to fall to zero. 



FIG. 30. Chamberland's Autoclave. 



8. Now open the vent cock slowly, and allow the 

 internal pressure to adjust itself to that of the 

 atmosphere. 



9. Remove the cover and take out the sterilised 

 contents. 



Sterilisation Periods. An exceedingly useful device 

 for the timing of sterilisation periods (and indeed for 

 many other operations in the laboratory) is the 



ELECTRIC SIGNAL TIMING CLOCK. 



This is a clock of American type in which the face 

 is surrounded by a metal plate having a series of 60 



