STERILIZATION — ANTISEPSIS — FOOD PRESERVATION 73 



presence of moisture; it is, therefore, preferable to use formal- 

 dehyde for room disinfection when possible. 



Alkalies, especially the caustics, sodium hydroxide and potas- 

 sium hydroxide, are powerful germicides. Commercial lye is also 

 valuable as a disinfectant. Perhaps the most important of the 

 alkalies is calcium hydroxide, Ca(0H)2 which, because of its 

 low cost, is extensively used for the disinfection of excreta. 



Lime. — The addition of o.i per cent of unslaked lime to fluid 

 cultures of the typhoid bacillus and cholera spirillum will render 

 them sterile in four or five hours. Typhoid dejecta are sterilized 

 in six hours when thoroughly mixed with 3 per cent of slaked lime; 

 the addition of 6 per cent will accomplish the same result in two 

 hours. A convenient form for practical use is an aqueous mix- 

 ture containing 20 per cent of lime — so-called milk of lime. 

 Typhoid and cholera dejecta are sterilized in one hour after mix- 

 ing with 20 per cent of this mixture. In practice it is safer to use 

 a considerable excess of lime. From the foregoing facts it would 

 seem'probable that lime or whitewash as ordinarily applied would 

 possess disinfectant properties. Experimental work has demon- 

 strated this to be a fact. The organisms of anthrax, glanders and 

 the pus cocci are destroyed within twenty-four hours by one 

 application. For spore-forming organisms and the bacUlus of 

 tuberculosis the poyyer is not so great, the latter organism not 

 being destroyed by three applications of the whitewash. Practi- 

 cally, whitewashing is an effective means of disinfecting wood- 

 work, perhaps because those microbes which are not killed at once 

 are caught in the whitewash and their further distribution 

 prevented. 



Oxidizing agents are usually germicidal. Chlorine, bromine 

 and iodine, ozone, nitric acid, potassium permanganate, chlorin- 

 ated lime, organic peroxides andperacids, and hydrogen peroxide, 

 belong to this class. Chlorine, employed as chlorinated lime, 

 is a valuable disinfectant for excreta. In the form of bleaching 

 powder it has been extensively used in the disinfection of drinking" 

 water and of swimming pools. Liquid chlorine is also employed 



