72 



DISINFECTANTS 



The alternative explanation is that the disinfectant 

 acts as a catalyst, speeding up the very slow denatura- 

 tion of some essential protein. Native proteins are never 

 stabile. With such catalytic action, the concentration 

 exponent need not be an integer, and it is usually greatly 

 affected by temperature. However, the determination of 

 n m disinfection is too inaccurate to permit decision be- 

 tween the two theories. 



3 % 



15 



L2' 



1.0. 

 0.9 

 08 



as 



Fig. 17. Effect of various concentrations of formaldehyde and of 

 phenol on the death time of Bacterium coli. Abscissa: death time, on 

 logarithmic scale; ordinate: per cent concentration, on logarithmic 

 scale. (Original data.) 



Concentration exponents have been measured occasion- 

 ally since Chick (1908) and Watson (1908) first called at- 

 tention to them. Only two extensive studies with large 

 numbers of experiments have been published, those of 

 Paul, Birstein and Reuss (1910) on different acids, and 

 those of Tilley (1939) on the phenol group. Paul and 

 associates used the method of death rates, Tilley the 

 method of death times. Some data by these and other 

 authors are shown in Table 15. 



Not only do the values of n fluctuate considerably in 

 different experiments, but Tilley found, with Bad. 

 typhosum and phenol, that they fluctuated in the same 



