208 



BARNETT COHEN 



The behavior of Bact. coli at different hydrogen ion concentrations 



and temperatures 



An inspection of the curves for the death of Bact. coli at pH 

 3.5 (fig. 7) shows that at 30°C. the curve is ahnost a straight fine 

 with a sUght suggestion of flattening out at the beginning. At 

 20°C. this flattening out is more pronounced, and at 10°C. and 

 0°C., still more so. These de\dations cannot be fuUy accounted 

 for by the probable experimental error, though the process of 



Fio. 8. Experiment 8. The Death Rate of Bact. coli in M/500 Phosphate 

 Buffer of pH 6.1 at 0°, 10°, 20°, 30°C. 



Parallel duplicate curves are omitted 



drawing 'smoothed' curves through the points may be made to 

 wipe out this deviation. We have found, in experiments not 

 detailed here, that at higher acidities these de\'iations from the 

 straight-line logarithmic decUne are absent so that the resulting 

 curves resemble those found for Bact. typhosum in experiment 6. 

 If we now refer to figures 8, 9 and 10, it will be observed that 

 these deviations are enhanced, especially for the lower tempera- 

 tures. Such deviations simply mean that as time progresses 



