i 9 2o] ROSE, KRAYBILL, fir ROSE— OXIDASE ACTIVITY 234 



3. Potassium, sodium, and magnesium nitrates (0.10N) 

 had practically no effect on oxidation, while nitrates of calcium, 

 barium, manganese, and iron (ferric) decreased it. 



4. Potassium chloride (0.02 N and 0.002 N) had no effect on 

 oxidation, while manganese chloride in these concentrations 

 increased it. 



5. Tartrates, oxalates, citrates, acetates, and carbonates 

 increased oxidation. Marked increase in oxidation in these cases 

 seems to be due, in part at least, to the low acidity of the mixtures 

 of bark, pyrogallol, and salt. 



6. Marked decrease in oxidation is not necessarily accompanied 

 by high acidity of the mixtures. 



7. Ions other than the hydrogen and hydroxyl may be important 

 in regulating oxidase activity. 



8. In neutralizing hydrogen or hydroxyl ions, it is important 

 to take into consideration, in the study of oxidase activity, the 

 possible effect of the salts formed thereby. 



9. The chlorides which retard the combustion of tobacco at 

 high temperatures also retard the oxidase action at low tempera- 

 tures. 



10. The effect of the alkali chlorides upon oxidase activity 

 suggests a practical application in preventing the browning of 

 fruits and vegetables during their preparation for canning, pre- 

 serving, or drying. 



The authors wish to express their appreciation to Dr. Wm. 

 Crocker for many helpful suggestions. 



Bureau of Plant Industry 

 Washington, D.C. 



LITERATURE CITED 



1. Abderhalden, Emil, and Guggenheim, Markus, Versuche liber die Wirk- 

 ung der Tyrosinase aus Russula dellca auf Ty rosin, tyrosinhaltige Poly- 

 peptide und einige andere Verbindungen unter verschiedenen Bedingungen. 

 Zeit. Physiol. Chem. 54:331-353. 1907-1908. 



2. Alsberg, Carl L., Beitrage zur Kenntnis der Guajak-Reaktion. Arch. 

 Exp. Path, und Pharm. Festschrift. Schmiedeberg, pp. 39-53. 1908. 



