STERILIZATION BY HEAT 



45 



Arnold steam sterilizer. This consists of a very shallow 

 boiling pan, a steam chamber, which is surrounded by 

 the removable hood, and a large pan, which catches the 

 drip water. The large pan is connected with the small 

 pan by a number of small openings, thus constantly 

 keeping a supply of water in the boiling pan. The ad- 

 vantage of this design is the rapidity with which steam 



Fig. 20. — Arnold steam sterilizer (Fowler). ~ 



is developed and the little attention the apparatus 

 requires when in operation. The temperature within 

 the steam chamber is approximately that of boiling 

 water, 212° F. This form of sterilizer is extensively 

 used to sterilize the various nutrient media used for 

 growing bacteria. In order to be certain that steriliza- 

 tion has been complete it is customary to sterilize these 



