390 
Journal of Agricultural Research 
Vol. XXVI, No. 9 
(447.2) when plotted give a series of points which can be used very 
readily in the quantitative determination of carotin. In Figure 2 the 
concentration of the solution is represented on the X-axis and the — log 10 
transmittancy on the Y-axis. It was found that readings could be more 
r, , t e r 
Fig. 2. —Comparison of graphs obtained by using the helium lines 447.2 and 501.6 and the mercury 
line 435-8- 
easily made using the mercury line, because of its greater brightness, but 
as far as transmittancies and concentrations are concerned the light from 
either mercury or helium is suitable. Light from the mercury line was 
used in most of the work, as this source of light is in more common usage 
and would be more readily available to anyone wishing to do similar 
work on the quantitative determination of carotin. 
COMPARISON OF THE ACCURACY OF READINGS OF THE MERCURY LINE 
435.8 AND HELIUM LINE 447-2 
It will not be out of place here to compare the results of determinations 
made by using the mercury line (435.8) and the helium line (447.2) on 
the same solutions of carotin in a 2 cm. cell. 
Table III.— Comparison a of quantitative determinations made, using helium and 
mercury light 
Scale. 
Transmit¬ 
tancy. 
Dilution. 
Carotin 
determined 
per liter, 
using graphs 
in figure 2. 
Hg. 435-81 
He. 447.2J 
^Soln. A. 
f O. 0799 
\ O. 0460 
20 X 
20 X 
Mgm. 
63. 0 
62.6 
Hg. 435-81 
He. 447 - 2 J 
[Sola. B...... :. 
f O. 1492 
\ O. 0970 
200 X 
200 X 
474.O 
474.O 
Hg. 435-81 
He. 447.2J 
^Soln. C. 
/ 0. 1175 
\ 0.0654 
500 X 
500 X 
h 335 * 0 
1,380.0 
° The data of this table should not be correlated with those of other tables. 
