HYDROGEN-ION CONCENTRATION OF BROTH MEDIA 



159 



n/20 NaOH. From the last figure, the formol number was 

 obtained. 



Formol number {F. N.): Milligrams of formol-titrating N per 

 100 cc. of culture. 



The results of the experiment are contained in the following 

 table : 



TABLE 8 

 Experiment IV 



As a result of autoclaving, slight increases in formol-titrating 

 nitrogen are manifest in every lot of broth excepting that adjusted 

 to Ph 9.2 which was the only flask to show any appreciable change 

 in Ph. The greatest increases in formol number are seen in the 

 lots which showed little or no reaction change. No change in 

 formol-titrating nitrogen occurs during the first seven days fol- 

 lowing autoclaving except in the 9.2 lot. Here a small increase 

 occurred. From the results of this one experiment it must be 

 concluded that changes in the Ph of broth as a result of autoclav- 

 ing and standing bear no relationship to changes in formol-titrating 

 nitrogen. The results are at variance with those reported by 

 Itano (1916a) in which decreases in the hydrogen-ion concentra- 

 tion of broth upon autoclaving appeared to be roughly correlated 

 with increases in formol-titrating nitrogen. It perhaps should be 

 noted that fewer changes in Ph were recorded in experiment IV 

 than were apparent in the earlier experunents. 



At present, the most logical explanation of acidity increase 

 noted in the various experiments would rest upon the observation 

 of Robertson that as the hydrolysis of a protein proceeds the base- 

 binding capacity of the material increases through the opening 

 up of the -COHN- group of the protein molecule. 



