PART II 



MODE OF ACTION OF DISINFECTANTS 

 AND ANTISEPTICS 



In the fight against bacteria, a rather surprising va- 

 riety of compounds is being used. There are oxidizing 

 agents like hydrogen peroxide or chlorine, reducing com- 

 pounds like sulfur dioxide, heavy metal salts such as 

 those of mercury and silver, light metal salts like sodium 

 fluoride or arsenate, acids like boric or salicylic, alkalies 

 such as slaked lime or trisodium phosphate, alcohols like 

 ethyl alcohol or phenol, amines, many dyes, and synthetic 

 or natural drugs. It is not possible that all these so 

 different compounds react with proteins in the same way. 

 However, they all lead to the same general result, the 

 inactivation of bacteria. This becomes understandable 

 if one considers that proteins are very large molecules 

 with many different ' ' side chains ' ' so that they offer the 

 possibility of a great variety of reactions which may have 

 the same outcome on the whole molecule. Native pro- 

 teins react very easily and promptly, and it is consis- 

 tent with chemical experience to assume that reactions 

 on many different side chains or atomic groups produce 

 the same physiological result, namely, the denaturation 

 of the protein, which thereby becomes unfit for further 

 biological function. 



The reason why so many different compounds are be- 

 ing used is of a practical nature ; it must be sought above 

 all in the various purposes for which they are employed. 

 Mercury compounds cannot be used to sterilize food; 

 salicylic acid will preserve acid fruits, but not neutral 

 meat; chlorine is an excellent disinfectant for water, 

 less efiicient in sewage, still less so when organic mat- 



