STANDARDIZATION OF DISINFECTANTS 



243 



representing the degree of dilution of the weakest strength of the 

 phenol control that kills within the same time. The same is done 

 for the weakest strength that kills in 1 5 min. The mean of the two 

 is the coefi&cient. The method of determining the coefficient will 

 be seen in Table III. 



Date: May 18, 191.^. 



TABLE III 



Name, "A." 



Temperature of medication, 20° C. 



Culture used, B. typhosus; 24 hr.; extract broth filtered. 



Proportion of culture and disinfectant, o.i cc. + s cc. 



Organic matter, none; kind, none; amount, none. 



Subculture media, standard extract broth. Reaction, + 1.5; quantity in each tube, 



10 cc. 



To Determine the Comparative Cost per Unit of Efficiency. — 



When bids are solicited for supplying disinfectants they should 

 be required to be made so as to show the comparative cost per 

 100 units of efficiency of the disinfectant as compared with 100 

 units of pure phenol. It is manifestly cheaper to purchase a 



17 



