Oct. is, 1920 Germicidal Value of Some Chlorin Disinfectants 



101 



adhere strictly to the rule; and coefficients were deduced at any time 

 within the 15-minute period, except that no coefficient was deduced 

 unless there was growth in the phenol subculture tubes after both 2% 

 and 5 minutes' exposure. This is really only a return to previous prac- 

 tice (7), and the results obtained are sufficiently accurate for all prac- 

 tical purposes. 



In all these tests, dilutions were based on the amount of available 

 chlorin; and it should, therefore, be understood that the coefficients are 

 really, so to speak, those of available chlorin as it is present in chloramin 

 T, eusol, Dakin's solution, and chlorin water. 



It should also be noted that in order to make the original solutions 

 more nearly equal in chlorin content the amount of bleaching powder 

 in proportion to water was the same for eusol as for Dakin's solution. 

 The amount used was 5 gm. to 250 cc, which follows the usual pro- 

 portion for Dakin's solution but varies from the usual proportion for 

 eusol. These original solutions were then diluted with distilled water to 

 obtain the desired amounts of available chlorin in the various dilutions. 



The results are summarized in Table XIV, the successive figures 

 from top to bottom in each column being coefficients obtained at various 

 times. It will be noted that they do not always agree perfectly, but 

 they are not offered as examples of accuracy. On the contrary, they 

 are to be considered as approximate values to be taken for what they 

 are worth as illustrations of the general principles of selective action 

 already shown to a greater or less degree in previous experiments. 



Table XIV. — Coefficients of chloramin T, Dakin's solution, eusol, and chlorin water, 

 based on tlie content of available chlorin 



In connection with preceding experiments solutions of chlorin T, 

 Dakin's solution, and eusol were kept in a dark closet at room temperature, 

 and titrations were made at intervals to detect any changes that might 

 occur. It was found that Dakin's solution and solutions of chloramin T 

 will keep for a month or more without any great loss of available chlorin; 

 while, on the other hand, eusol deteriorates rapidly, there being a notice- 

 able change even within 24 hours. For example, in one instance a sample 

 of Dakin's solution showed only about 10 per cent loss after standing 6 

 187932°— 20 2 



