Feb. 1, 1925 
The Quantitative Determination of Xanthophyll 
259 
Table III.— Colorimetric readings show¬ 
ing determinations made on the same 
solution at different times of the day 
Lovibcnd 
Milli- 
Depth in 
slide 
grams 
mm. when 
readings in 
of 
compared 
terms of 
xantho- 
with 
milligrams of 
phyll 
Date and 
Lovibond 
xanthophyll 
per 
time of day 
slides 
per liter of 
liter of 
solution 
solution 
5 
10 
20 
5 
10 
20 
Aver- 
age 
September 
6, 9 a. m- 
0.8 
1.3 
1.7 
33.2 
33.0 
41.2 
35.8 
7, 9 a. m_ 
.9 
1.3 
2.2 
30.4 
33.0 
32.0 
31.8 
6, 10 a. m... 
.9 
1.3 
1.9 
30.4 
33.0 
36.8 
33.4 
7,10 a. m.. * 
.9 
1.3 
2.3 
30.4 
33.0 
30.8 
31.4 
6, 11 a. m..- 
.9 
1.3 
2.2 
30.4 
33.0 
32.0 
31.8 
7, 11 a. m... 
.8 
1.3 
2.3 
33.2 
33.0 
30.8 
32.3 
6, 12 m_ 
.9 
1.4 
2.1 
30.4 
30.6 
33.4 
31.5 
7, 12 m_ 
.8 
1.4 
2.3 
33.2 
30.6 
30.8 
31.5 
6, 1 p. m- 
.8 
1.3 
2.1 
33.2 
33.0 
33.4 
33.2 
7, 1 p. m_ 
.9 
1.4 
2.2 
30.4 
30.6 
32.0 
31.0 
6, 2 p. m_ 
.8 
1.3 
2.2 
33.2 
33.0 
32.0 
32.7 
7, 2 p. m_ 
.7 
1.2 
2.1 
37.2 
35.4 
33.4 
35.3 
6, 3 p. m- 
.8 
1.2 
2.1 
33.2 
35.4 
33.4 
34.0 
7, 3 p. m_ 
1.0 
1.3 
2.4 
26.6 
33.0 
29.6 
29.7 
6, 4 p. m_ 
.8 
1.3 
1.9 
33.2 
33.0 
36.8 
34.3 
7, 4 p. m.. 
.9 
1.3 
2.1 
30.4 
33.0 
33.4 
32.3 
Table IV.— Spectrophotometric read¬ 
ings showing the determinations on 
the same solution as that used in 
Table III , at different times of the 
day. ( 2-centimeter cell and mercury 
line 1+85.8 mg. used ) 
1 
I 
Time of day 
Transmit- 
tancy 
Dilution 
Milligrams 
of xantho¬ 
phyll per 
liter of 
solution 
9 a. m__ 
0.191 
20 x 
34.4 
10 a. jn_ 
.184 
20 x 
35.2 
11 a. m. 
.184 
20 x 
35.2 
12 m_ 
.182 
20 x 
35.4 
1 p. m_ 
.182 
20 x 
35.4 
2 p. m_ 
. 186 
20 x 
34.8 
3 p. m_ 
.184 
20 x 
35.2 
4 p. m_ 
. 185 
20 x 
35.0 
Such results as these obtained for 
xanthophyll as well as those obtained 
for carotin reported in a previous pa¬ 
per certainly militate against the use 
of the colorimeter for accurate work 
on the quantitative measurement of 
the plant pigments xanthophyll and 
carotin. 
THE SPECIFIC TRANSMISSIVE IN¬ 
DEX OF XANTHOPHYLL 
The specific transmissive index ( Jc ) 
for xanthophyll in ether can be calcu¬ 
lated from the graph in Figure 2 by 
using the equation 
-logioj 
be 
Table V.— The specific transmissive 
index of xanthophyll 
t 
(c) Con¬ 
centration 
in 
centigrams 
per liter 
-logioT 
Figure 
obtained 
from right- 
hand side 
of graph 
», 
i Thick- 
; ness of 
! cell 
, 
k 
0.400 
1.671 
1 Cm. 
j 2 i 
2.089 
.320 
1. 337 
2 
2. 089 
.220 
.919 
2 | 
2.088 
. 140 
.585 
2 i 
2.089 
. 100 
.418 
: 2 | 
2.090 
Average _ 
! 
2.089 
The average value for K, the specific 
transmissive index, for xanthophyll in 
ether is 2.089 for the mercury line 
435.8 mg The specific transmissive in¬ 
dex for carotin was found 7 to be 1.986 
in ether, using the mercury line 435.8 mg 
as the light source. 
RELATIVE POSITION OF THE EDGES 
OF THE ABSORPTION BANDS (i) 
OF CAROTIN AND XANTHOPHYLL 
Since pure pigments were available 
it was believed that some value might 
be derived from curves drawn showing 
the position of the edge, nearer the 
green, of the absorption band in a Hil- 
ger wave-length spectrometer (constant 
deviation type). Readings (Tables 
VI and VII), using a narrow slit and 
a 200-watt lamp as the source of white 
light, in mg are plotted on the Y-axis in 
Figure 5, while the amount of carotm 
and xanthophyll present per liter is 
indicated on the X-axis. The quartz 
glass cells used had widths of 10, 20, 
and 60 millimeters. The chief value 
of these curves lies in the fact that they 
may be used in the identification of an 
unknown pigment as carotin or as 
xanthophyll. 
7 SCHERTZ, F. M. THE QUANTITATIVE DETERMINATION OF CAROTIN BY MEANS OF THE SPECTROPHO¬ 
TOMETER and the colorimeter. Jour. Agr. Research 26: 383-400, illus. 1924. 
