DISINFECTANTS 



95 



the data of Charlton and Levine on the death of spores 

 of B. Metieus is shown in Figure 21. 



Fig. 21. Relation between chlorine concentration and death time of 

 spores of B. metiens at various acidities. Abscissa: Concentration of 

 chlorine, on logarithmic scale; ordinate: time required to kill 99% 

 of the spores. (From data of Charlton and Levine, 1937.) 



Iodine is used extensively in medicine as a disinfec- 

 tant. As it is almost insoluble in water, it is applied 

 either in alcoholic solution or in aqueous potassium iodide 

 solution. Strangely enough, no experiments could be 

 found which would permit a calculation of the concen- 

 tration exponent. Nor has any study of the etfect of 

 acidity on iodine disinfection been made, as far as the 

 author is aware. Whether iodine acts as such, or as 

 HOI (corresponding to the HOCl of chlorine) or as KL 

 in the solutions with potassium iodide, is not known. 



8. Soaps. The mechanism of disinfection by soaps 

 is rather complicated. Not only does their efficiency de- 

 pend upon two variable factors, namely, the proportion 

 of the various fatty acids, and the amount of excess 

 alkali, but they have also a highly selective action, lethal 



