Dec. i, 1923 
393 
Quantitative Determination of Carotin 
Table VI .—Specific transmissive index for carotin 
Concentra¬ 
tion (CM 
— logioT 
Thickness (6). 
Constant ( k ). 
IN PETROLEUM ETHER OR IN 95 PER CENT ALCOHOL. 
O. 400 
O.37O 
O. 29O 
O. 130 
O. O7O 
I- 530 
I. 418 
1. no 
0.499 
0. 268 
2 cm. 
2 cm. 
2 cm. 
2 cm. 
2 cm. 
Average.... 
I. 912 
I. 916 
9 T 3 
1. 919 
1. 914 
1. 9148, or 1. 915 
IN ETHER. 
0. 400 
O.37O 
O. 290 
O. I3O 
O. 070 
1-585 
1.467 
1.150 
0.519 
0. 281 
2 cm. 
2 cm. 
2 cm. 
2 cm. 
2 cm. 
Average.... 
1.981 
1. 982 
1. 982 
1.996 
2. 007 
1.9896, or 1. 990 
a Cgm.per liter. 
The pure carotin used for obtaining the data was prepared, in general, 
according to the methods of Willstatter. The carotin was obtained from 
carrots, crystallized several times from alcohol and finally recrystallized 
from a carbon disulphide solution by the addition of petroleum ether. 
The purity of the sample was determined by means of the melting point 
(174 0 C.) and by means of the transmittancy of the solutions. That 
preparation of carotin a solution of which absorbed the greatest amount 
of mercury light per unit of concentration was regarded as the purest 
obtainable. The specific transmissive index for carotin as obtained for 
ether is based upon the results for three different preparations and three 
different weighings of carotin, after considerable preliminary investiga¬ 
tion. The complete details of the preparation of carotin will appear in 
a paper which will follow. 
brief outline of the procedure for the DETERMINATION of carotin 
BY THE SPECTROPHOTOMETRIC METHOD 
The carotin is obtained in ethereal or petroleum ether solution in 
the method 11 of its separation and is ready for spectrophotometrical 
examination. The carotin solution is made up to some convenient 
volume, for example, 100 or 500 cc. It will most likely be necessary to 
make dilutions from this, for the solution used in the spectrophotometer 
must contain not more than 4 milligrams of carotin per liter, because 
greater concentrations will give a transmittancy which can not be used 
in obtaining data from the graphs in Figure 3. 
11 The method will be described in a later paper. 
