FOOD-COLORING SUBSTANCES. 



47 



Table 3. — Behavior of colors wTien treated loith reducing agents followed by oxidizing 



agents — Continued . 



No. 



Coloring 

 matter. 



With sodium hydrosulphite. 



Coloring 

 matter. 



Reduction product with air or 

 slum persulphate. 



potas- 



76 



517 



Much paler (\vith 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 Ovith excess). 



*523 



Color restored. 





81 



9 



Decolorized. 



2 



Remaius colorless or nearly so. 





82 



*3 



Decolorized. 



*3 



Remains colorless or nearly so. 





83 



6 



Daik; then pale. 



6 



Pale reddish. 





84 



534 



( Alk. sol.), red, slowly. 



SSi 



Color restored. 





85 



***707 



Not reduced. 



^^^for 







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 



BroT\T2er; then colorless. 



277 



Remains colorless or neai'Iy 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 



(539 



Decolorized. 



639 



Color restored. 





100 



*5.84 



Decolorized. 



*584 



Color restored. 





101 



**448 



Decolorized. 



**448 



Color restored. 





102 



***425 



Not decolorized. 



*!=*425 







103 



426 



Not decolorized. 



426 







104 



=f=**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 



***5(H 



Not decolorized. 



***S04 







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 difi'erences exist, depending on 

 wh{!ther the solutions are practically neutral or markedly acid. 

 They must not be alkahne and should be free from foreign material, 

 though dissolved amyl alcohol, etc., does not interfere. With the 

 oil-soluble <lyes, 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" of the azo colors, for which, of course, well- 

 krxjwn reduction methods msiy also ]n\ applied. The test is made 

 as follows: About 5 cc of the dye solution (pref(a'al)ly of concentra- 

 tion id the neighborhood of from 0.005 to 0.01 per cent) are treated 

 with })romin water (1 per cent) added (h-op ])y drop until a little 

 mon; lius been used tlian is required to destroy tlui (ly(^. A few drops 

 of 3 per cent hydrazin sulphate solution are then added and the mix- 



