Mar. 15,1925 Physical and Chemical Properties of Xanthophyll 
583 
been repeated; the results are given in 
Table IX. This experiment was made 
in order to test the effect of light upon 
the oxidation of the yellow pigments in 
other as well as to test the keeping 
qualities of the carotinoids in this sol¬ 
vent. The ether in this case was care¬ 
fully redistilled to remove peroxides; 
experiments were run using both caro¬ 
tin and xanthophyll. The rate of oxi¬ 
dation of the two pigments in pure 
ether under exactly the same condi¬ 
tions ought to serve as a good index of 
their respective rates of oxidation. 
The solutions were made up using 
pure pigments. One sample of each 
solution was stored in the ice box and 
one of each was allowed to stand in the. 
sunlight during part of the day. The 
amount of each pigment in the two so¬ 
lutions was determined colorimetri- 
cally and spectrophotometrically on 
the dates indicated in Table IX. 
Carotin is seen to be more stable 
than xanthophyll in the dark in the ice 
box, although the reverse is true in sun¬ 
light at room temperature. In each 
case the ether used was exactly the 
same and, consequently, the results 
should be absolutely comparable. 
in the case of xanthophyll.” The 
purity of all the pigments used by 
Ewart has been seriously questioned 
(5 ). Consequently, his work is of 
doubtful value regarding the yellow 
pigments reported here. 
In researches on the carotin and 
xanthophyll content of green and 
yellow leaves, Goerrig (4) found that 
the yellow pigment content of dried 
leaves (Fagus silvatica) was affected 
considerably by temperature and light 
during the drying process, as the fol¬ 
lowing data show: 
30° dark 
90° dark 
Sunlight, 
room 
tempera¬ 
ture 
Carotin _ 
33 
25 
17 
Xanthophyll _ 
59X2 
28X2 
55X2 
At the higher temperature xantho¬ 
phyll appears to be more sensitive 
than carotin, while in sunlight carotin 
is affected more than xanthophyll. 
Willstatter and Stoll (12, p. 105) 
found on the examination of a carotin 
Table IX .—Oxidation of pure ether solutions of xanthophyll and of carotin 
XANTHOPHYLL 
In the dark in the ice box 
In sunlight at room temperature 
Date 
Dilution 
Trans- 
mittancy 
Mgm. per 
liter 
Per cent 
unoxid¬ 
ized 
Dilution 
Trans- 
mittancy 
Mgm. per 
liter 
Per cent 
unoxid¬ 
ized 
May 1 _ 
Times 
10 
0.206 
16.5 
100 
Times 
10 
0.206 
16.5 
100 
May 11 _ 
10 
.239 
14.9 
90.3 
2 
.065 
5.7 
34. 
May 24 _ 
10 
.343 
10.8 
65.4 
0 
.629 
.47 
2 . 
July 21_ 
0 
.222 
1.5 
9.4 
Oxidized completely. 
CAROTIN 
May 1 _ 
5 
0.405 
4.80 
100 
5 
0. 405 
4.8 
100 
May 11 _ 
2 
.132 
4. 42 
92 
0 
.364 
1.1 
22.4 
May 24 _ 
2 
.213 
3. 34 
69.6 
Completely oxidized on May 17. 
July 21_ 
0 
.375 
1. 03 
21.4 
The oxidation or rate of bleaching 
of these two carotinoids has been 
observed by several authors. Ewart 
(2, p . 187) states that “pure samples 
of xanthophyll oxidize and bleach 
much more slowly in the light than do 
impure samples, xanthophyll being 
less readily oxidizable than chlorophyll 
and very much less so than carotin,” 
and ( p . 188 ) “using watery emulsions 
of carotin exposed to light and air, the 
oxidation was much more rapid than 
solution (0.0134 gm. in 0.5 liter of 
petroleum ether containing a little 
alcohol) stored in a well-stoppered 
bottle in the dark for three weeks that 
it had lost no color. A xanthophyll 
solution (0.0142 gm. in 0.5 liter of 
ether) quickly bleached; they believed 
this to be due to impurities in the 
ether. After two days an ether solu¬ 
tion lost 5 per cent and after three 
weeks 60 per cent of its color. They 
state (p. 243) that an ether solution of 
