52 DESTRUCTION OF BACTERIA BY CHEMICALS 



disinfectant chiefly because it forms new insoluble 

 odorless compounds. 



It is not very irritant when taken into stomach, but 

 vapors cause considerable annoyance in the eyes, nose, 

 and mouth. The lower animals resist it considerably, 

 but insects are not affected. It is more effective in 

 the presence of moisture and when the temperature is 

 high, up to 120 F. If these conditions cannot be 

 obtained the exposure must be longer. Two and one- 

 half per cent, by volume of the aqueous solution or 

 1 per cent, by volume of gas are sufficient to destroy 

 fresh virulent cultures of the common non-spore-bearing 

 bacteria in a few minutes. 



Carbolic Acid or Phenol. This is a crystalline solid 

 which softens when exposed to the air. It is soluble 

 in 15 parts of water. It must be thoroughly mixed with 

 material to be disinfected. It is not destructive to 

 fabrics or colors. It acts best at about the body 

 temperature. It is not much affected by the presence 

 of organic substances. A 5 per cent, solution kills 

 spores in a few hours, and 1 to 1000 inhibits the growth 

 of all bacteria and may be considered as an antiseptic; 

 3 per cent, solutions kill the pus cocci in one minute. 



Cresols. These are thick sticky brown fluids related 

 to carbolic acid. They make a milky emulsion with 

 water. The best known ones are tricresol, creolin, 

 and lysol. The two latter are probably the best, as 

 they mix with water fairly well. All these substances 

 in 5 per cent, emulsion kill the ordinary bacteria 

 within three minutes and the spore-formers within an 

 hour. 



