Feb. 1,1925 
The Quantitative Determination of Xantho'phyll 
261 
Table VI.— Position of the edge of the absorption band (I) of xanthophyll in an 
ethereal solution 
Milligrams of xanthophyll per liter ® 
Thickness of 
solution 
2.3 
4.7 
9.4 
14.1 
18.1 
28.2 
42.3 
56.4 
Mm. 
mu 
mu 
mu 
mu 
mu 
mu 
mu 
mu 
10... 
480.9 
485.2 
490.1 
493.1 
495.0 
498.1 
500.7 
502.5 
20... 
484.8 
490.1 
495.1 
497.7 
499.5 
502.1 
505.8 
507.2 
€0... 
487.5 
491.3 
496.8 
499.6 
502.0 
504.8 
508.1 
510.1 
• Each figure is an average of five or more settings. 
Table VII.— Position of the edge of the absorption band (I) of carotin in an ethereal 
solution 
Thickness of solution 
Milligrams of carotin per liter B 
2.3 
4.7 
9.4 
18.8 
37.6 
47.0 
10_ 
Mm. 
mu 
485.1 
mu 
488.4 
mu 
493.7 
mu 
501.4 
mu 
506.8 
mu 
508.0 
20_ 
489.9 
494.1 
500.0 
506.0 
510.9 
512.8 
60_ 
491.4 
497.4 
501.9 
507.6 
513.9 
515.6 
® Each figure is an average of five or more settings. 
By testing the behavior of a sub¬ 
stance suspected of being either carotin 
or xanthophyll, toward a mixture of 
petroleum ether and methyl alcohol 8 
and then determining the amount of 
pigment present per liter by use of the 
spectrophotometric or colorimetric 
graphs (figs. 2 and 3), in connection 
with the graphs (fig. 5) showing where 
the edge of the band should come, it is 
easily possible to distinguish carotin 
from xanthophyll. Solutions of carotin 
and solutions of xanthophyll of known 
concentrations were taken and it was 
found that it was possible to dis¬ 
tinguish them by means of Figure 5 
alone, that is, by the position of the 
edge of the absorption bands. It may 
also be possible to tell whether a certain 
yellow solution contains carotin or 
xanthophyll, or neither. 
SUMMARY 
Graphs are given for various con¬ 
centrations of xanthophyll in com¬ 
parison with Lovibond slides 5, 10, 
and 20, yellow. From these graphs 
the amount of xanthophyll in a solu¬ 
tion may be determined. 
The transmittancy of xanthophyll 
in ether has been determined for the 
mercury line 435.8 mu. A graph has 
been drawn from which it is possible 
to determine very accurately the 
amount of xanthophyll in an ether 
solution. 
The specific transmissive index for 
xanthophyll in ether solution is 2.089, 
while that for carotin was found to be 
1.986. The mercury line 435.8 mp was 
used in the determinations. 
Data have been submitted which 
show that the spectrophotometer is 
accurate to 10 parts in 354 or 2.8 per 
cent, while the colorimeter is accurate 
to 61 parts in 358 or 17.0 per cent. 
A graph (fig. 5) has been made 
showing the relative position of the 
edge of the absorption band (I) for 
carotin and for xanthophyll. These 
may be used to ascertain whether a 
solution contains carotin or xantho¬ 
phyll, after the concentration has been 
determined. 
8 Carotin will separate in the petroleum ether layer while xanthophyll will be found in the methyl 
alcohol layer. 
13951—25t-5 
