STAKDARDIZATION OF DISINFECTANTS 257 



1000 by simply adding the required parts of distilled water, 

 using small quantities, thus: 



10 parts of I : 10,000 + i part water = i :ii,ooo 

 10 parts of I : 10,000 + 2 parts water = i : 12,000 

 10 parts of I ; 10,000 + 3 parts water = i : 13,000 

 Etc. 



Any other quantity proportions may be used, however, as 

 10, 15, 20, etc., parts of the substock solution with the required 

 parts of distilled water. If the i : 1000 substock solution is to 

 be used then the dilutions should be increased by 100, as follows: 



10 + I = I :iioo 

 10 + 2 = I : 1200 

 10 + 3 = I :i300 

 10 + 4 = I : 1400 



or any other equal proportion of stock solution and distilled water 

 may be used, as 



5 + 0.5, 100 + 10, or 1000 + 100, etc. 



If the highest stock dilution (i : 100,000) is to be used, then the 

 increase should be 10,000, thus: 



10 + I = I : 110,000 

 10 + 2 = I : 120,000 

 10 + 3 = 1: 130,000 



Determining the Phenol Coefficient 



Having determined that dilution which gives the same coagula- 

 tion opacity as the 5 per cent. carboHc acid, it is a very simple 

 matter to determine the phenol albumen coagulating coefficient 

 by simply dividing the strength of the dilution of the disinfectant 

 tested by the phenol dilution (1:20). 



The following are the coagulating coefficients of a few dis- 

 infectants : 



