1 40 Journal of Agricultural Research voi. xv, no. 3 



amount of oxygen delivered in any given time was read in the gas burette. 

 The amount of ground material used for each experiment varied from 

 0.5 to 0.025 gm., depending upon the catalase activity of the tissue. In 

 general 0.14 gm. gave a delivery rate suitable to t?he size of the apparatus, 

 and except when otherwise stated t^hat is the amount used for each 

 determination in this paper. Bolting cloth of 70 to 80 mesh to the inch 

 was found most desirable. This degree of pulverizing gave the maxi- 

 mum activity for Johnson grass, although finer grinding (100 mesh to 

 the inch) gave somewhat higher activity for the clover. 



Dioxogen (H2O2 12 V.), of the Oakland Chemical Co., was used almost 

 exclusively in these experiments, but two other brands of hydrogen 

 peroxid were also tried, peroxid of hydrogen, 3.10 per cent, of the Oak- 

 land Chemical Co., and hydrogen peroxid, 2.7 per cent, of the J. T Baker 

 Chemical Co. The Bureau of Chemistry furnished the following pharma- 

 copeial analyses of these peroxids : 



Peroxid of hydrogen {Oakland Chemical Co.) 



Available H2O2 2 .77 per cent. 



Nonvolatile matter in 20 cc 0.021 gm. 



Acidity, 25 cc 1.4 cc. Nfio. 



No preservative detected. 



Hydrogen peroxid, C. P. (J. T. Baker Chemical Co.) 



Available H2O2 2 .92 per cent. 



Nonvolatile matter, 20 cc 0.036 gm. 



Acidity, 25 cc 1.77 cc. Njio 



Acetanilid (declared i part in 7,000) i part in 18,000. 



Dioxogen {Oakland Chemical Co.) 



Available H2O2 3.63 per cent. 



Nonvolatile matter, 20 cc o.oii gm. 



Acidity, 25 cc 0.9 cc. Njio. 



No preservative detected. 



It is interesting to compare the percentage of HjOg found in these 

 peroxids by the pharmacopeial method with the percentages calculated 

 from the amount of gas delivered upon adding an excess of seed catalase. 

 In the determinations with catalase 2 gm. of the unneutralized peroxid 

 was diluted with 3 cc. of distilled water, and to this was added an emul- 

 sion of 1.5 gm. of powdered crimson-clover seeds in 5 cc. of water. The 

 gas delivered was reduced to standard pressure and temperature and 

 its weight calculated upon the assumption that it was all oxygen. From 

 this the percentage of HjOj in the peroxids was then calculated. The 

 values given in every case are the average of two or more closely 

 agreeing determinations. These percentages are shown in Table I. 



It is seen that the catalase determinations are somewhat larger in 

 every case and that the percentage excess is about constant. This 

 discrepancy is probably due to a consistent error in one or the other of 



