CHEMICAL STERILIZATION AND DISINFECTION. 91 



materials harmless are : heat, either by burning, by 

 steaming for from half an hour to an hour, or by boil- 

 ing in a 2 per cent, sodium carbonate solution for fifteen 

 minutes ; 3 to 4 per cent, solution of commercial car- 

 bolic acid ; milk of lime, and a solution of chlorinated 

 lime (" chloride of lime ") containing not less than 0.25 

 per cent, of free chlorine. The chloride of lime from 

 which such a solution is to be made should be fresh 

 and of good quality. Good chlorinated lime, as pur- 

 chased in the shops, should contain not less than 25 to 

 30 per cent, of available chlorine. The materials to be 

 disinfected in either of the lime solutions should remain 

 in them for about two hours. The solutions should be 

 freshly prepared when needed, as they rapidly decom- 

 pose upon standing. 



