DISINFECTANTS 21 



where it also acts as a deodorant and desiccant. Under certain 

 circumstances it is one of the most powerful germicides known. 

 One per cent solution will kill most bacteria in one to five min- 

 utes. A 5 per cent solution usually kills all spores within an 

 hour. Unfortunately it bleaches and destroys fabrics. 



Recently, chlorinated lime or chlorinated soda has come into 

 prominence as a disinfectant of drinking water. Very minute 

 quantities will render a comparatively clean water sterile. 



Labarraque's Solution contains several chlorine compounds, 

 chiefly sodium hypochlorite and sodium chloride. It is a little 

 more expensive and not so efficient as chlorinated lime. 



Antiformin consists of a solution of caustic soda and chlorinated 

 lime. It is a strong germicide ; a 2 to 5 per cent solution will kill 

 most vegetative forms in five minutes. The tubercle bacillus and 

 other members of the same group, however, are slightly affected 

 by it. 



Chlorine Gas is strongly germicidal. Its activity is due to the 

 fact that in the presence of moisture it combines with the hydro- 

 gen, thus liberating oxygen which in its nascent state combines 

 with the albuminous substance of the bacterial cell. A 0.2 per 

 cent watery solution kills spores in 5 minutes and the vegetative 

 forms almost immediately. 



Iodine has much the same value as chlorine both in its gaseous 

 state and in solution. 



Acids are effective germicides. A 1 to 500 solution of sulphuric 

 acid kills most vegetative forms in an hour. Hydrochloric acid 

 is somewhat weaker; acetic, citric, and salicylic acids are much 

 weaker still. A 2 per cent boric acid solution will destroy the 

 less resistant forms of bacteria. 



Sulphur Dioxide is a strong insecticide but is of little value 

 as a germicide. The slight action it possesses on bacteria depends 

 on the presence of moisture. It has no effect upon spores. 



Application of Disinfectants. The most effective place to 

 apply disinfectants is as near the seat of the origin of infection as 

 possible. As the excretions from the mouth, nose, and bowels, 

 as well as discharges from eruptions or wounds, are mainly respon- 



