THE PRACTICE OF DISINFECTION 153 



Steam Under Pressure. When water is heated in 

 an open vessel or one loosely covered that is, at at- 

 mospheric pressure the temperature cannot go above 



Fig. 47. Autoclave sterilizer. Except in form, the autoclave differs 

 but slightly from the full-jacketed sterilizer (Fig. 22, page 46). 

 It is made of heavy copper with solid cast brass self-sealing door; 

 the safety-valve is set to relieve at 15 pounds, and the jacket extends 

 entirely around the chamber. The pressure, however, cannot be 

 retained in the jacket while the door is open. Surgical dressings 

 when withdrawn from the autoclave are dry. The latent heat of 

 the steam at the high pressure will evaporate any moisture from the 

 steam instantly upon exposure to the atmosphere. 



212 F. (100 C.), but when heated in a tightly closed 

 container both the temperature and pressure increase, 

 so that a temperature of 130 C. and more, according 

 to the amount of pressure employed, may be reached. 



