8 



the influence of the hydrogen ion concentration upon tlie amylase 

 of malt ^). 



The dissociation constant of the acid appears to be the same as 

 for the amylase of Aspergillus, that of the base on the contrary is 

 bigger i.e. =r 5.76 X 10— ^^ So as an acid the two amylases are 

 equally strong, as a base that of the malt is the weakest. 



Further investigations on other sorts of amylase will perhaps 

 instruct us, if pointing out their differences in this way will be of 

 any value. 



Utrecht, November 1921. Botanical Laboratory. 



LITERATURE. 



1. SöRENSEN S. P. L., Biochem. Zeitschr. Bd. 21, 1909. Enzymstudien II. 



2. MiCHAELis, L., Biochem. Zeitschr. Band 33, 1911. Ueber die Dissoziation der 

 amphoteren Electrolyte. 



3. MicHAELis L. und Davidsohn, Biochem. Zeitschr. Band 35, 1911. Die Wir- 

 kung der H. Ionen auf das Invertin. 



4. RiNGEE, W. E. en Trigt H. van, Onderzoek. Physiol, lab. der Un. Utrecht. 

 5e reeks, dl. 14, 1913. Over den invloed van de reactie op de werking van ptyaline. 



5. MiCHAELis L. und Pechstein, H., Bioch. Zeitschr. Band 59, 1914. Die 

 Wirkungsbedingungen der Speicheldiastase. 



6. Adler, L., Biochem. Zeitschr. Band 77, 1916. Ueber den Einfluss der Was- 

 serstoffionen auf die Wirksamkeit der Malzdiastase. 



7. Clark, W. M. and Lubs, H. Am., Journ. of Bact. Vol. II. 1917. The colori- 

 metric determination of hydrogen ion concentration and its applications in bacteriology. 



1) It might be doubted if the iodine reaction method is accurate enough to get 

 exact results. 1 therefore refer to those of Adler (6) who determined the hydro- 

 lysis of amylum by means of rotation and reductive power. The numbers he 

 obtained appear to give a curve nearly identical to mine. 



