Dec. i, 1923 Quantitative Determination of Carotin 391 
Quantitative determinations were made on three solutions (A, B, and 
C) of different concentrations. These are recorded in Table III. The 
results obtained are concordant indicating that either the Hg. or He. line 
may be used. 
THE EFFECT OF SOLVENTS UPON TRANSMITTANCY; TRANSMITTANCY OF A 
SOLUTION OF PURE CAROTIN 
Often, it is convenient to have the carotin dissolved in petroleum 
ether or alcohol instead of ether and, consequently, some knowledge of 
the influence of these three solvents upon the transmittancy seemed 
desirable. The solutions were made as follows: There were dissolved 
21.0 mgm. of carefully purified carotin in 250 cc. of petroleum ether. 
Fig. 3.—Comparison of graphs of the transmittancies of identical concentrations of carotin in petro¬ 
leum ether, alcohol and ether, using the mercury line 435-8. 
Of this solution 2.5 cc. were then diluted to 50 cc. with petroleum 
ether, ether, or alcohol, and all further dilutions were made with the 
same respective solvents. 10 It will be noted that the ether and alcohol 
solutions contain small percentages of petroleum ether. The results are 
given in Table IV and are plotted in Figure 3. 
In Figure 3 the effect of the solvents is seen. The ethereal solution 
of carotin transmitted somewhat less light than did the alcohol or the 
petroleum ether solution. The graphs for the petroleum ether and the 
alcohol solutions coincide. Since the results (Table IV) for ether were 
obtained from two different weighings and preparations of carotin and 
checked within the limits of error, they have been used as the basis 
for quantitative determinations. 
To check the accuracy of the graph for the carotin sample given in 
Figure 3, 42.0 mgm. of a third specially purified sample of carotin were 
10 The petroleum ether used here was the fraction which boils at 30-50° C., the ether was U. S. P. and 
the alcohol absolute. 
