H. ECKWEILER, H. M. NOYES, AND K, G. FALK 301 



The results have been presented without introducing the correction 

 used by Tague in his work in which the amount of acid or alkali 

 required to bring the solution without solute to a definite hydrogen ion 

 concentration was subtracted from the amount required with the 

 solute present. This corrected value would give a more nearly ac- 

 curate measure of the reaction between amino-acid, etc., and acid 

 or alkali. For the results given here, this correction is negligible 

 except for the largest additions of acid or alkali. If desired, the data 

 given in Column 1 of Table I will permit the introduction of these 

 corrections. 



With regard to the isoelectric point results given in Table II, the 

 determinations by the potentiometer method, that is the determina- 

 tion of the hydrogen ion concentrations of the solutions with neither 

 acid nor alkali added, cannot lay claim to any great degree of accu- 

 racy for the amino-acids since the buffer action is so slight and since 

 a broad zone exists on the curve where traces of acid or alkali may 

 change the results appreciably. With the dipeptides this zone is nar- 

 rower and the results should be correspondingly more accurate. The 

 indicator method appears to give somewhat more accurate results as 

 fewer manipulations are required. However, too much stress must 

 not be placed upon their exactness. 



Discussion of Results. 



The data given refer to one concentration (0.05 m) for each sub- 

 stance. This naturally limits for the present the general applicability 

 of the conclusions. 



Michaelis^" and others^® have developed the theoretical interpre- 

 tation of such titration curves and applied their conclusions to the 

 results of a number of substances. Among other applications, they 

 have considered the relations to the acid and basic dissociation con- 

 stants of the ampholyte, to conditions for the smallest and greatest 

 buffer actions, etc. In this paper, the discussion will be limited 

 to questions which have been discussed briefly or not at all by 

 others. 



^^ Cf. Clark^ for the general treatment and for complete references. 



