gram of phenolpkthalein in 1 c. c. of absolute alcohol. 1 c. c. X 10 
sodium hydroxide, and 5 e. e. of water, immediately and after twenty - 
four hours, with the following results: 
READINGS OX COLORIMETER. 
! Quantity 
of -odium 
hvdroxide 
‘ X/50. 
Immedi- 
ately. 
After 24 
hours. 
Standard. 
c.c. 
1 
5 
6 
5 
2 
5 
6.3 
5 
3 
4.8 
7.5 
5 
4 
5 
i . i 
5 
5 
4.9 
9.3 
5 
Similar experiments were tried using X 500 sodium hydroxide in the 
proportion of 1. 2, 3. 4, and 5 c. c. at a total dilution of 7 c c. The fol- 
lowing results were obtained on comparison with the phenolphthalein 
standard employed in the previous series of experiments: 
READINGS OX COLORIMETER. 
Quantity 
of sodium Immedi- 
hydroxide ately. 
X 500. 
After 24 
hours. standard. 
c.c. 
1 12 
Colorless. 5 
2 6.5 
8. 8 5 
3 5.5 
6.4 5 
4 5. 5 
5.9 5 
5 5 
5. 9 5 
It would seem, therefore, that, so far as the influence of alkali on 
the fading of the phenolphthalein color is concerned, the most rapid 
fading occurs either with verv small or with very large amounts of 
alkali. With very small amounts of alkali the fading out of the color 
is doubtless due to the absorption of carbon dioxide from the air in 
sufficient amounts to decompose the colored salt, and in the case of 
larger amounts of alkali the fading is probably connected with the 
formation of a colorless salt-like body from the colored quinoid sub- 
stance. Regardless of any theory of the process, the fact remains that 
the presence of alkali may be responsible for the fading out of the 
phenolphthalein color encountered in our own experiments with blood. 
Still, a third factor involved in the fading of the phenolphthalein 
color is the presence of hydrogen peroxide. That such is the case, is 
indicated by the fact that in those experiments in which blood alone is 
employed to effect the oxidation of phenolphthalin in alkaline solution, 
tne depth of color persists unchanged for a much longer interval of 
