76 



DISINFECTANTS 



TABLE 16 



Temperature coefficients of disinfection 

 I. Disinfection 'by various alcohols. (From Tilley, 1942) 



II. Disinfection by chlorine at various acidities. (From Charlton 

 and Levine, 1937) 



///. Disinfection by high acidity, at pH 3.5. (From Cohen, 1922) 



logarithms of the death times are plotted against tem- 

 perature. Figure 18 shows a few of Chick's data plotted 

 in this way. The curves representing the different phenol 

 concentrations are nearly parallel, indicating the same 

 Qio, whereas the curve for AgNOa has a different slope, 

 which means that the reaction has a different Qio. 



For practical purposes, it is customary to determine 

 which concentrations will . produce the same degree of 

 sterilization at different temperatures. McCulloch (1936) 

 found that Bact. typhosum will be killed in 10 minutes 

 at 2° by 2.0% phenol, at 20° by 1.18% and at 40° by 0.56%. 



