582 
Journal of Agricultural Research, voi. xxx, no. 6 
Table VII. — Oxidation of xanthophyll (in dry form) 
SAMPLE EXPOSED TO LIGHT (ROOM TEMPERATURE) 
Days 
Date 
Spectrophotometric data 
Colorimetric data 
Trans- 
mit- 
tancy 
Volume 
Xan¬ 
tho¬ 
phyll 
per 
sample 
Xan¬ 
tho¬ 
phyll 
unoxi¬ 
dized 
Lovibond slide, yellow 
Volume 
Xan¬ 
tho¬ 
phyll 
per 
sample 
5 
10 
20 
0 __ 
Mar. 31 
Apr. 8 
Apr. 15 
Apr. 22 
Apr. 29 
May 6 
c. c. 
Mgm. 
1. 05 
.58 
. 18 
.13 
.037 
.012 
Per cent 
100 
55.2 
17.1 
12.3 
3.5 
i.i 
C.c. 
Mgm. 
1. 05 
.56 
(“) 
. 14 
( a ) 
(°) 
7. 
0.324 
.178 
.271 
.237 
' .633 
500 
100 
100 
25 
25 
4.4 
12.2 
5.0 
7.5 
20.5 
7.2 
12.3 
100 
14_ 
21 .. 
13.0 
25 
28_ 
35_ 
SAMPLE KEPT IN DARK (ROOM TEMPERATURE) 
0. 
Mar. 31 
1. 05 
100 
| 
7__ 
Apr. 8 
0 . 216 
500 
.79 
75.2 
3.1 
5.5 
9.1 
ioo ! 
14___... 
Apr. 15 
.088 
200 
.50 
47.9 
4.5 
7.1 
11.8 
100 j 
21 __ 
Apr. 22 
.012 
200 
.44 
41.9 
3.1 
4.9 
8.0 
50 
28_ 
Apr. 29 
.027 
100 
.37 
35.2 
3.1 
5.4 
8.5 
50 ! 
35.. 
May 6 
.137 
125 
.25 
23.8 
2.4 
3.8 
6.3 
25 
° Too dilute to estimate. 
Table VIII. — Oxidation of carotin (in dry form) 
SAMPLE EXPOSED TO LIGHT (ROOM TEMPERATURE) 
Days 
Date 
Spectrophotometric data 
Colorimetric data 
! Trans- 
[ mit- 
tancy 
Vol¬ 
ume 
Carotin 
per 
sample 
Carotin 
unoxi¬ 
dized 
Lovibond slide, yellow 
Vol¬ 
ume 
Carotin 
per 
sample 
Per 
cent 
5 
10 
20 
C.c. 
Mgm. 
Per cent 
C. c. 
Mgm. 
0 _ 
May 1 
0. 443 
500 
0.44 
100 
1.3 
2.1 
3.8 
25 
0.43 
100 
7.. 
May 8 
.129 
125 
.28 
63.6 
2.3 
3.5 
5.9 
25 
.27 
62.8 
14_ 
May 15 ! 
.238 
125 
.19 
43.1 
3.2 
5.2 
7.8 
25 
.19 
44.1 
21 .... 
May 22 | 
.401 
125 
.12 
27.3 
5.3 
8.3 
12.6 
25 
.11 
25.5 
31_i 
June 1 ! 
125 
6.0 
9.6 
14.7 
25 
.09 
20.9 
40_ 
June 10 
Completely oxidized. 
SAMPLE KEPT IN DARK (ROOM TEMPERATURE) 
0 . 
1 ' ! 
_1 May 1 
0.443 
500 
0.44 
100 
1.3 
2.1 
3.8 
25 
Q. 43 
100 
7_ 
_ May 8 i 
.0813 
125 
.34 
78.4 
2.0 
3.1 
4.5 
25 
.30 
69.7 
14_ 
May 15 ! 
.0982 
125 
.32 
72.7 
2.1 
3.1 
5.2 
25 
.28 
65.1 
21 _ 
_ May 22 ' 
.145 
125 
, .26 
59.0 
2.2 
3.7 
6 . 4 
25 
.25 
58.1 
31_ 
_i June 1 
125 ! 
2.3 
3.6 
6.2 
25 
.25 
58.1 
91. j Aug. 1 Completely oxidized. 
Table III. The samples (0.44 mgm. 
of carotin in each evaporating dish) 
were treated exactly like those for 
xanthophyll as described above. 
Both the colorimeter and the spectro¬ 
photometer were used in making the 
determinations. The xanthophyll was 
dissolved in 95 per cent alcohol and the 
carotin in high-boiling petroleum ether; 
on these solutions the colorimetric and 
spectrophotometric determinations 
were made. Carotin is seen to be less 
readily oxidizable than xanthophyll in 
light as well as in darkness at room 
temperature. 
Carotin has been shown (9) to oxi¬ 
dize quite readily in absolute anhy¬ 
drous ether. Since the ether was not 
redistilled to remove certain objection¬ 
able impurities this experiment has 
