252 BACTERIOLOGICAL METHODS 



THE ALBUMEN COAGULATING COEFFICIENT OF 

 DISINFECTANTS 



As is well known to surgeons and pathologists, the action of 

 disinfectants and their value in tissue disinfection and in the 

 disinfection of organic matter such as sputum, excreta, etc., 

 varies according to their albumen coagulating power. Some 

 disinfectants, as alcohol, mercuric chloride, silver nitrate, copper 

 sulphate and others, coagulate albumen very actively and this 

 property checks or prevents further penetration and action. 

 Furthermore, inert combinations between the coagulating dis- 

 infectants (metallic ions) and ' the albuminous substances are 

 formed which render a portion of the disinfectant unavoidable for 

 further action. This behavior explains why some disinfectants are 

 more active when diluted, as for example alcohol and carbolic acid. 

 Even high dilutions of copper sulphate (i : 50,000 to i : 4,000,000) 

 will gradually kill bacteria in water or in other nonorganic liquids, 

 due to a coagulation of the bacterial plasm, whereas solutions of 

 5 per cent, to 10 per cent, of the same substance are considered 

 rather unsatisfactory disinfectants. The stronger solutions 

 coagulate the albuminous matter in which the bacteria may be 

 imbedded, no doubt quickly killing the organisms in the exposed 

 outer layers of the albuminous particles or masses while the 

 layer of coagulum encloses many of the bacteria effectually pro- 

 tecting them against further action of the disinfectant. These 

 enclosed bacteria may become liberated after a time due to a 

 breaking up of the coagulated covering or coating and, if patho- 

 genic, may cause a single infection or an epidemic. 



The following are some of the disinfecting agents which pre- 

 cipitate or coagulate albumen actively: 



Alcohol. Chloral hydrate. 



Ether. Phenol. 



Salts of heavy metals. Picric acid. 



Camphor. Mineral acids. 



Volatile oils. Some organic acids. 

 Tannic acid. 



