540 OXIDATION FERMENTS 



f erred to note the fact that frequently the iodine reaction is 

 noticeably weaker with blood than with many of the tissues, 

 this point then serving to suggest the presence of a true per- 

 oxidase in the tissue apart from the blood which may be in 

 them. 7 The use of e thy Ihydr op er oxide in place of hydrogen 

 peroxide is undoubtedly a step in advance, as it is not 

 affected by tissue catalases. 



Oxidation of Formic Acid. Another method for the de- 

 tection of peroxidases in tissues, for which credit is due 

 F. Battelli and L. Stern, depends on the ability of the tissues 

 of higher animals to oxidize formic acid in vitro in the pres- 

 ence of hydrogen peroxide with production of carbonic acid 

 (H.COO H + = CO 2 + H 2 0) . By the use of this method, 

 by determining the C0 2 , it has been shown that the liver more 

 than other tissues has a particularly strong power of oxidiz- 

 ing formic acid. 8 



Purpurogallin Method. A gravimetric method recom- 

 mended for estimating peroxidases, used frequently by Bach 

 and Chodat, depends on the oxidation separation of the rela- 

 tively insoluble purpurogallin from a solution of pyrogallol. 



Phenolphthalin Method. In the experiments carried on 

 with E. v. Czyhlarz the author has performed many estima- 

 tions by the phenolphthalin method of Kastle and Shed. 9 It 

 was found that the oxidation transformation of the colorless 

 phenolphthalin into phenolphthalein with its brilliant red 

 color in alkaline solution is well adapted to spectrophotome- 

 tric measurement, a sharply defined absorption band occur- 

 ring about the middle of the spectrum. However, the use- 

 fulness of the method is decidedly impaired by the fact that 

 an alkaline solution of phenolphthalin may rapidly undergo 

 spontaneous reddening in the presence of hydrogen- 

 peroxide. 



7 F. Battelli and L. Stern (Geneva), Biochem. Zeitschr., 18, 49-59, 1908. 



8 F. Battelli and L. Stern (Geneva), Biochem. Zeitschr., 18, 44, 1908; 

 Z. Sarafoff, Dissert. Univ. of Geneva, 1908, cited in Jahresber. f. Tierchem., 39, 

 528, 1909. 



Kastle and Shed, Amer. Chem. Jour., 26, 26, 1901. 



