FOOD-COLORING SUBSTANCES. 
47 
Table 3.- 
-Behavior of colors when treated with reducing agents followed by oxidizing 
agents — Continued . 
No. 
Coloring 
matter. 
With sodium hy&rosulphite. 
Coloring 
matter. 
Reduction product with air or 
sium persulphate. 
potas- 
76 
517 
Much paler (with excess). 
517 
Color restored. 
77 
518 
Much paler (with excess). 
518 
Color restored. 
78 
520 
Much paler (with excess). 
520 
Color restored. 
79 
521 
Much paler (with excess). 
521 
Color restored. 
80 
*523 
Much paler (with excess). 
*523 
Color restored. 
81 
2 
Decolorized. 
2 
Remains colorless or nearly so. 
82 
*3 
Decolorized. 
*3 
Remains colorless or nearly so. 
83 
6 
Dark; then pale. 
6 
Pale reddish. 
84 
534 
(Alk. sol.), red, slowly. 
m 
Color restored. 
85 
***707 
Not reduced. 
***707 
86 
*10 
Decolorized. 
*10 
Remains colorless or nearly so. 
87 
*468 
Decolorized. 
*468 
Color restored. 
88 
464 
Decolorized. 
464. 
Color restored. 
89 
438 
Almost decolorized. 
438 
Color restored. 
90 
**433 
Paler. 
**433 
Greener. 
91 
442 
Paler, slowly. 
442 
Restored. 
92 
476 
Not readily reduced. 
476 
93 
240 
Almost decolorized. 
240 
Remains colorless or nearly so. 
94 
277 
Browner; then colorless. 
277 
Remains colorless or nearly so. 
95 
562 
(Alk. sol.), yellow. 
562 
Color restored. 
96 
658 
No change. 
658 
97 
496 
Almost decolorized. 
496 
Color largely restored. 
98 
650 
Decolorized. 
650 
Color restored. 
99 
639 
Decolorized. 
639 
Color restored. 
100 
*584 
Decolorized. 
*584 
Color restored. 
101 
**448 
Decolorized. 
**448 
Color restored. 
102 
***425 ' 
Not decolorized. 
***425 
103 
426 
Not decolorized. 
426 
104 
***451 
Decolorized. 
***451 
Color restored. 
105 
452 
Decolorized. 
452 
Color restored. 
106 
*#427 
Decolorized. 
**427 
Color restored. 
107 
428 
Decolorized. 
428 
Color restored. 
108 
*197 
Almost decolorized. 
*197 
Colorless or nearly so. 
109 
*201 
Almost decolorized. 
*201 
Colorless or nearly so. 
110 
17 
Decolorized. 
17 
Remains colorless or nearly so. 
111 
18 
Decolorized. 
18 
Remains colorless or nearly so. 
112 
505 
Not decolorized. 
505 
113 
499 
Not decolorized. 
499 
114 
***504 
Not decolorized. 
***504 
115 
502 
Not decolorized. 
502 
OXIDATION WITH BROMIN. 
This test is valuable for quickly testing the color solutions obtained 
in the fractionation. The free acid need not be removed ; though, as 
described in detail below, minor differences exist, depending on 
whether the solutions are practically neutral or markedly acid. 
They must not be alkaline and should be free from foreign material, 
though dissolved amyl alcohol, etc., does not interfere. With the 
oil-soluble dyes, the oxidation should be made in acetic acid of from 
50 to 80 per cent strength. 
The chief practical use of the test is for the detection of the azo 
and the azin dyes, especially when in admixture with natural coloring 
matters. It provides the simplest means for the identification of 
the " first component' 7 of the azo colors, for which, of course, well- 
known reduction methods may also be applied. The test is made 
as follows: About 5 cc of the dye solution (preferably of concentra- 
tion in the neighborhood of from 0.005 to 0.01 per cent) are treated 
with bromin water (1 per cent) added drop by drop until a little 
more has been used than is required to destroy the dye. A few drops 
of 3 per cent hydrazin sulphate solution are then added and the mix- 
