6-hydroxy-5-(2-methoxy-5-methyl-4-sulfophenylazo)-2-naphtalenesulfonic acid sodium salt.
Related dyes are FD&C Yellow #6:
FD&C Yellow #6
the food color Scarlet GN, FD&C Red #4:
FD&C Red #4: Scarlet GN
the food color tartrazine, or FD&C Yellow #5:
FD&C Yellow #5: Tartrazine
Red 40 is used in many products, such as orange soda, as a coloring agent.
Yellow #5 and #6 are widely used in candies and drug coatings. Orange B is used in hotdog and sausage casings.
Some people are sensitive to yellow #5, and their reactions to it are severe enough that prescription medicines that contain it must be labeled specially. None of the other certified dyes have this special requirement.
The dyes on this group are known as azo dyes, because they have the two nitrogen atoms together in the center (called an azo group).
These dyes were originally manufactured from coal tar, but are now mostly made from petroleum.
Azo dyes come in many colors besides those allowed in food (listed above). The other colors find use in fabrics, paper products, and plastics.
orange B: InChI=1/C22H18N4O9S2.2Na/c1-2-35-22(28)20-19(21(27)26(25-20)13-7-9-14(10-8-13)36(29,30)31)24-23-17-11-12-18(37(32,33)34)16-6-4-3-5-15(16)17;;/h3-12,23H,2H2,1H3,(H,29,30,31)(H,32,33,34);;/q;2*+1/p-2/fC22H16N4O9S2.2Na/q-2;2m