Dec. z, 1923 
Quantitative Determination of Carotin 
389 
The mercury line (576.9+579.1) was found to be unsatisfactory for 
solutions of a concentration less than 42.0 mgm. per liter, for the trans- 
mittancies obtained were not of sufficient accuracy and gave values 
which did not show great enough differences to insure accuracy in the 
determinations, in other words, the graph line would be too nearly parallel 
with the X-axis. 
Readings for the mercury line (576.9+579.1) give transmittancies 
which are of no use for quantitative work, while those for the line 546.1 
offer greater promise. In the case of the mercury lines (576.9 + 579.1) 
(see Table I) practically all of the light was transmitted by the con¬ 
centrations used (0.0 to 42.0 mgm. per liter), while line 546.1 was trans¬ 
mitted to too great an extent for accurate quantitative work; concentra¬ 
tions as great as or greater than 8.4 mgm. per liter transmitted none of 
the mercury light at wave length 435.8. 
Since the results obtained from using the mercury line 435.8 appeared 
very favorable (Table I), another experiment was made with solutions 
which contained less than 8.4 mgm. per liter, the results of which are 
given in Table II. Concentrations of 8.4 mgm. per liter and above could 
not be used because of total extinction at the scale setting of 435.8. 
Transmittancies were also obtained for the helium lines 447.2 and 501.6. 
Since, from Table I, it was observed that the concentrations used 
were too great for light in the blue regions and also because of the fact 
that the light from the helium tubes is not as bright as that of mercury 
vapor, lower concentrations were chosen for the work. 
Table II .—Preliminary experiments on the transmittancy a of a solution of carotin (in 
U. S. P. ether) 
Wave length and light source. 
Transmit¬ 
tancy. 
Carotin per 
liter. 
| Mgm . 
IT Of A'i e.§ . 
0. 0034 
7. 560 
0. 0156 
5. 040 
O. 1320 
2. 520 
O. 3650 
I. 260 
0. 5920 
O. 630 
O. 7040 
0-315 
He. AA *7 . . 
0. 0063 
5 . 040 
O. 0871 
2. 520 
O. 2850 
I. 260 
O. 5110 
O. 63O 
O. 6220 
0.315 
He. 501.6. 
O. 0756 
12. 600 
O. 1200 
IO. 080 
O. 2 IOO 
7. 560 
1 
3530 
S- 040 
O. 59OO 
2. 520 
O. 7740 
I. 260 
O. 887O 
O. 630 
! 
O. 86lO 
0.315 
a These data should not be correlated with data in other tables, as the figures here were used only in the 
search for a suitable wave length and a suitable concentration of the pigment. The concentration 0.315 mgm. 
as seen in fig. 2 gave low transmittancy values for all three wave lengths of light; this fact shows that the 
error was due to dilution and not to reading the instrument. 
The results obtained for the helium lines as well as for the mercury 
line, reported in Table II, and the graphs of the values of - log 10 trans¬ 
mittancy when plotted against concentration, are illustrated in Figure 2. 
The transmittancies for the mercury line (435.8) and the helium line 
