THE BLOOD AS AN OXYGEN-CARRIER IN THE OXIDATION OF PHENOL- 
PHTHALIN BY HYDROGEN PEROXIDE. 
THE REACTION AND MODE OF PROCEDURE. 
Phenolphthalin or dioxytriphenylmethane carbonic acid is the leuc-o 
compound of phenol phthalein. On oxidation, it passes into pheno- 
phthalein in the sense of this equation: 
QoH^O.+O = C 20 H li O i -hH 2 O. 
Hence, if the oxidation takes place in alkaline solution, we have the 
production of a deep purplish red compound (phenolphthalein in alkali) 
from a colorless salt. The oxidation of phenolphthalin may be accom- 
plished by various peroxides, such as lead and manganese peroxide, 
benzoyl peroxide, etc., and by the plant oxidases. In fact. Ka>tle and 
She-dd® several years ago proposed a neutral solution of this compound 
as a reagent for the plant oxidases. Phenolphthalin is also slowly 
oxidized by hydrogen peroxide in neutral and alkaline solution. As is 
the case with many of the oxidations of this character, however, the 
change is greatly accelerated by various oxygen-carriers, such as plati- 
num black, etc., and as indicated in the foregoing, by the peroxidase of 
blood. It will be seen from our results, which are given in the fol- 
lowing pages, that when allowed to stand alone an alkaline solution of 
phenolphthalin and hydrogen peroxide gives only a faint pink colora- 
tion. If, however, a very small quantity of blood be added to such a 
solution it soon acquires the deep, purplish red coloration, character- 
istic of phenolphthalein in alkah. indicating that under the influence 
of blood or an oxygen-carrier, hydrogen peroxide is able to effect the 
oxidation of phenolphthalin with far greater rapidity than when 
allowed to react alone. 
That a certain amount of free alkali is essential to this change mav 
be gathered from the following: Six solutions were prepared, each 
containing 2 c. c. of fresh blood solution (Porch, normal), 1 cu. mm. to 
250 c. c. and 5 c. c. of a reagent, containing 0.032 gram phenolphthalin, 
0.0034 gram hydrogen peroxide, and 1 c. c. N 10 sodium hydroxide, 
the whole diluted to 100 c. c. To three of the mixed solutions 1 c. c. 
of water was added. These three solutions were labeled A. To each 
of the remaining solutions 1 c. c. of X 10 sodium hvdroxide was added. 
These solutions containing the excess of sodium hydroxide were 
« Arner. Chem. Jour., 26 1901 , 526-539. 
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