124 DISINFECTION— STERILIZATION— DISINFECTANTS 



immediately above the water. Surgical instruments may 

 be most conveniently sterilized by boiling or by steaming in 

 especially constructed instrument sterilizers. If boiled, the 

 addition of carbonate of soda, about 1 per cent., usually 

 prevents injury. 



Fig. 80. — A battery of two horizontal autoclaves in one of the author's 

 student laboratories. Steam is furnished direct from the University central 

 heating plant. 



Steam under pressure affords a much more rapid and cer- 

 tain method of destroying organisms. Fifteen to twenty 

 pounds' pressure corresponding to temperatures of 121° to 

 125° is commonly used. Variations depend on the bulk and 

 nature of the material. Apparatus for this purpose may now 

 be obtained from sizes as. small as one or two gallons up to 

 huge structures which will take one or two truckloads of 



