Oct. 21, 1918 Catalase and Oxidase Content of Seeds 141 



the series of determinations, but the possibility remains that the catalase 

 may split some of the H2O2 into hydrogen and oxygen. On the basis of 

 the first and the more likely assumption it seems probable that catalase 

 gives a complete decomposition of H2O2. 



The biologist needs to know the concentration of the hydrogen 

 peroxids he uses, whether they are used as sterilizing agents, forcing 

 agents for dormant seeds, or for catalase determinations. He will find 

 the catalase method sufficiently accurate and easily run with materials 

 at hand. The determination can be made without neutralizing the 

 acidity of the peroxids, even when it is rather high. The great excess 

 of the plant powder used (probably acting as a buffer), along with the 

 dilution of the peroxids, sufficiently counteract the inhibiting effects of 

 the acids to give complete decomposition. 



We have found dioxogen a desirable brand of hydrogen peroxid for 

 catalase determinations and for use as a forcing agent for dormant 

 seeds. It bears a rather high percentage of HjOo. The concentration 

 runs almost constant for different bottles of the same lot (date cut into 



Table I. — Percentage of H2O2 in hydrogen peroxids 



the label) and for bottles of different lots so far as our examinations 

 have gone. Its acidity is also low and about constant. 



Before using a bottle of dioxogen we always determined the percentage 

 of H2O2 in it. We also neutralized portions of it to phenolphthalein as 

 they were to be used. The 5 cc. employed in each catalase determina- 

 tion is capable of delivering about 65 cc. of oxygen at the temperature 

 of the experiment. The concentration of catalase and time was so 

 adjusted that in general not more than one-half the oxygen was deliv- 

 ered in an experiment, thus giving a great excess of hydrogen peroxid. 



EXPERIMENTAL WORK 

 EFFECT OP ACIDITY 



Various workers (7, 30) have mentioned the sensitiveness of catalase 

 to acids and have pointed out the fact that maximum activity and 

 minimum destruction occur in a neutral or slightly alkaline medium. 



