The activity of invertase in acid solutions, which are not strong 

 enough to destroy the enzym, was measured for hydrochloric, hydro- 

 bromic, nitric, phosphoric, sulphuric, boric, oxalic, tartaric, citric, 

 and acetic acids ; the activity depends almost entirely on the concen- 

 tration of hydrogen ions in the acid solution and the various acids 

 thus show typical differences which correspond with their recognized 

 degrees of "dissociation. The activity of invertase is zero in alkaline 

 solutions, rises to a maximum in very weakly acid ones, and de- 

 creases with stronger acidity. 



[Cir. 55] 



