10 
It is evident from these results that the oxidation of phenolphthalin 
by blood and hydrogen peroxide takes place only in alkaline solution, 
and a comparison of the 15-minute, two, and three hour series with one 
another goes to show that on standing in contact with hydrogen per- 
oxide and the sodium salt of phenolphthalin at the concentration indi- 
cated above, the blood loses a great deal of its oxygen-carrying power 
at the same time that it probably effects the decomposition of the 
hydrogen peroxide catalytically. (See the work of Jolles and Oppen- 
heimer.) With the view of throwing still further light on these 
points, 2 c. c. of blood solution (1 cu. mm. blood to 250 c. c.) were 
added to solution A of the three-hour series and to solution B of the 
same series 2 c. c. of distilled water. These solutions were then 
allowed to stand at ordinary temperature and at the end of fifteen 
minutes and one hour the depth of color of each determined in the 
colorimeter in the manner already described with the following results: 
READINGS ON COLORIMETER. 
Time. 
15 minutes 
1 hour 
A. 
B. 
12.7 
8.6 
6 
9 
Comparing the numbers under A with those given under A in the 
three-hour series, we note a remarkable increase in the depth of color 
and hence an increase in the amount of phenolphthalin oxidized, as 
the result of adding the second 2 c. c. of blood solution, thereby showing 
that while all other substances needful to effect the oxidation of the 
phenolphthalin were at hand in solution A of the three-hour series 
the oxygen carriers of the first portion of blood solution had been 
so altered by standing in contact with hydrogen peroxide and the sodium 
salt of phenolphthalin as to become largely incapable of effecting the 
oxidation. 
It has also been observed that within certain limits the oxidation of 
phenolphthalin by blood and hydrogen peroxide is nearly proportional 
to the concentration of the sodium hydroxide. That such is the fact 
may be seen from the following: Two solutions were prepared and 
labeled (1) and (2). (1) contained 0.032 gram phenolphthalin, 0.0031 
gram hydrogen peroxide, 30 c. c. 2s 100 sodium hydroxide, the whole 
made up to 100 c. c. with distilled water. (2) was the same as (1) 
except that it contained 21 c. c. N 10 sodium hydroxide. Bearing in 
mind that 10 c. c. X 100 or 1 c. c. X 10 sodium hydroxide are required 
respectively to neutralize the phenolphthalin present in these two- 
solutions, it will be seen that the free alkali in (1) and (2) corresponds 
to 20 c. c X 100 and 20 c. c. X 10 sodium hydroxide respectively. In 
order to determine the effect off alkali at these two concentrations on 
