THE PLANT OXIDASES 239 



GRAVIMETRIC METHOD OF CHODAT AND BACH. 



Among the most successful attempts to examine quanti- 

 tatively the action of oxidases of the laccase class are those 

 of Chodat and Bach (1904), who weighed the purpurogallin 

 formed under standard conditions from the interaction of 

 pyrogallol and hydrogen peroxide in the presence of a 

 peroxidase. 



The following table illustrates the precision of their 

 determinations, as well as the effect of varying the quanti- 

 ties of the substances which interact: 



TABLE LVII. 



EFFECT OF VARYING QUANTITIES OF ENZYME, PEROXIDE AND 

 PYROGALLOL. 



I. Pyrogallol, 1 gramme; hydrogen peroxide, 0-1 gramme; peroxidase, 

 from 0*01 to 0-1 gramme in 50 c.c. 



Weight of peroxidase: 



0-01 0-02 0-03 0-04 0-05 0-06 0-07 0-08 

 Weight of purpurogallin formed: 



0-021 0-042 0-066 0-083 0-102 0-123 0-145 0-166 



II. Pyrogallol, 1 gramme; peroxidase, 0-1 gramme; hydrogen peroxide, 

 from 0-01 to 0-1 gramme. 



Weight of peroxide: 



0-01 0-02 0-03 0-04 0-05 0-06 0-07 0-08 

 Weight of purpurogallin formed: 



0-020 0-042 0-060 0-078 0-099 0-121 0-142 0-168 



III. Peroxidase, 0-1 gramme; hydrogen peroxide, 0-1 gramme; pyro- 

 gallol, 1 to 4 grammes. 



Weight of pyrogallol : 



1-0 1-5 2-0 3-0 4-0 

 Weight of purpurogallin formed: 



0-168 0-205 0-203 0-208 0-202 



The results obtained by Chodat and Bach make it clear 

 that the weight of pyrogallol oxidized is proportional both 



