158 LAUEENCE F. FOSTER AND SAMUEL B. RANDALL 



the increase in COOH groups and Sorensen concluded that the 

 increased base-binding power was due to the formation of pep- 

 tides. T. B. Robertson (1918) has studied rather intensively 

 the changes in hydrogen-ion concentration which take place dur- 

 ing the hydrolysis of certain proteins and concludes that the power 

 to bind acids and bases resides in the -COHN- groups, inasmuch 

 as the protein molecule does not contain a sufficient number of 

 terminal -COOH and -NH2 groups to account for its high combin- 

 ing capacity for acids and alkalies. While bound up in the pro- 

 tein molecule these groups do not assist in the neutralization of 

 acids and bases but during hydrolysis the bonds are opened and 

 the binding capacity is increased. 



Itano (1916a) has reported an increase in formol-titrating nitro- 

 gen in media upon sterilization and has apparently shown that 

 at least a rough proportionality exists between the change in Ph 

 (increase) and the increase in amino acids as measured by the 

 method of Sorensen. 



With the view to ascertaining whether or not the changes in Ph 

 found in the experiments described could be correlated with an 

 increase in COOH groups produced through hydrolysis of the 

 peptone or protein of the broth the following experiments were 

 carried out: 



Experiment IV. The relationship between Pu changes in media and 

 changes in formol-titrating nitrogen 



Five lots of beef infusion broth were adjusted to Ph values 

 ranging from 5.2 to 9.2 and each lot distributed in three 30 cc. 

 portions. The Ph and formol number were determined: (1) 

 before autoclaving; (2) after autoclaving; (3) after seven days 

 standing at room temperature. 



Technic of formol titration, Kendall, Day, and Walker (1913): 

 Five cubic centimeters of the broth was diluted with 50 cc. of dis- 

 tilled water and 1 cc. of phenolphthalein (1 per cent alcoholic 

 solution) was added. The material was titrated to a faint pink 

 with n/20 NaOH or n/20 HCl. Five cubic centimeters of 

 neutral formalin were then added and the mixture allowed to 

 .stand for thirty minutes after which it was again titrated with 



