MATILDA M. BROOKS 179 



Experiments were carried out for 2 hours, after which time the 

 rate of production of CO2 remained practically constant for several 

 hours. For this reason it was not thought necessary to include in the 

 figures the data obtained after 2 hours. It is assumed that when 

 the course of the reaction reached this point equilibrium was attained. 



Fig. 1 shows the effect upon the rate of production of CO2 by 

 Bacillus butyricus when varying amounts of H2SO4 are added to the 



Rate of CO production 

 100%-oj.o 



6.7 



<5 Curve A 



^ Curve C 



« CURVCO 



60 



MINUTES 



Fig. 1. Curves showing the progressive eflFect of acid upon the pH value and 

 upon the rate of production of CO2 by B. butyricus (expressed as per cent of 

 the normal). The point marked zero on the abscissae indicates the initial pH 

 value and the rate of CO2 production of the bacteria at the instant before acid is 

 added. The figure attached to the first reading indicates the pH just after the 

 addition of acid; subsequent figures indicate the pH values at the times when the 

 readings were taken. The normal rate (which is taken as 100 per cent) represents 

 a change in the pH value of the indicator tube in the apparatus from 7.8 to 7.6 

 in a number of seconds, depending upon the amount of bacterial suspension used, 

 when the pH value of the organisms was 7.0. Each curve represents a single 

 typical experiment. 



