MECHANISM OF DEATH 365 



Paul, Birstein and Reuss (1910c) also give a large number of 

 temperature coefficients for the death of Micrococcus by hydrochloric 

 acid. 



Recently, this problem has been treated with a different technique 

 by Cooper and Haines (1929), and these authors thought they had 

 proved that three different groups of disinfectants existed, one show- 

 ing no temperature coefficient at all, one with a normal one, and one, 

 very high, ranging from 8 to 20 for an increase of temperature from 

 20°C. to 37°C. Their technique was practically that of the phenol 

 coefficient, for they measured the concentrations just sufficient to kill 

 the bacteria in thirty minutes. The temperature coefficient was 

 obtained by dividing one concentration by the other. 



This method of computing the temperature coefficient is not 

 permissable, because it impUes that the disinfectant action is pro- 

 portional to the concentration while we have seen in the preceding 

 chapter that this is by no means always the case. The error of these 

 authors can be shown easily by going back to our standard equation 

 for the death rate, on p. 347 



At37°C: KiCiH = log 



At20°C: K2C2H = log ~ 







In the endpoint method, log r is constant, t was experimentally, 

 equalized to thirty minutes, therefore 



KiCx- = K2C2- 



The relation between the two death rates is given by the formula 

 (p. 127). 



K\ = KiQn 



where Qn is the temperature coefficient for the increase in tempera- 

 ture from 20°C. to 37°C. 



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