172 MASS. EXPERIMENT STATION BULLETIN 167. 



Determination of Hydrogen Ion Concentration as Growth pro- 

 gressed. 



For this purpose 20, of the 50 cubic centimeters of the medium which 

 had been pipetted out from each flask, were used. The results will be 

 given in terms of Ph. 



Table XI. — Following the Change of Hydrogen Ion Concentration. 



' Pjl or exponent of hydrogen ion concentration. 



