DISINFECTANTS 19 



is perhaps one of the most generally used disinfectants because 

 it is so little affected by albuminous substances, it is not readily 

 decomposed, and does not harm fabrics, metals, or wood. 



Alcohol. Ten per cent solution inhibits bacterial growth ; 

 absolute alcohol kills vegetative forms within twenty-four hours. 



Formalin is a 40 per cent solution of formaldehyde gas; it is 

 supposed to have about one half the germicidal power of carbolic 

 acid ; a 2 per cent solution of formalin will kill vegetative forms in 

 from five to thirty minutes. 



Formaldehyde is probably of greatest service in its gaseous 

 form as a disinfectant of buildings and furniture. It does not 

 harm delicate fabrics; wood, copper, brass, and silver are not 

 affected by it. Under ordinary circumstances its powers of pene- 

 tration are not great and it can only be depended on for surface 

 disinfection. Vegetative forms of bacteria exposed directly to the 

 action of concentrated formaldehyde gas are killed at once. It 

 is advisable, however, in disinfecting a room to allow several hours' 

 exposure in order that the gas may reach all corners. It has very 

 little effect upon animals or insects. 



lodoform as such has little effect upon bacteria. When in the 

 presence of pus it is broken down into iodine compounds which 

 act partly by rendering inert the poisons produced by bacteria 

 and partly by destroying the bacteria themselves. 



Chloroform will destroy bacteria in the vegetative form in 1 

 per cent solution. It is not known to have any effect upon spores. 



Lysol is a coal-tar product containing about 50 per cent cresols. 

 It is generally used in 1 per cent solution; it has about double 

 the strength of carbolic acid. 



Bichloride of Mercury, commonly known as corrosive sublimate, 

 is one of the most potent germicides known. Exposure for half 

 an hour to a solution of 1 part to 2000 parts of water in the absence 

 of organic material, or 1 part to 1000 if it be present, is ample to 

 destroy all vegetative forms. Spores are killed in 1 to 500 solu- 

 tion in one hour. The value of bichloride of mercury is somewhat 

 limited by the fact that it is irritating to the skin, that in the pres- 

 ence of alkaline albuminous substances it forms inert compounds, 



