D&C Red No. 34.

Calcium salt of 3-hydroxy-4-[(1-sulfo-2 -naphthalenyl)azol-2-naphthalenecarboxylic acid. Sum of volatile matter (at 135 °C) and chlorides and sulfates (calculated as sodium salts), not more than 15 percent. 2-Amino-1-naphthalenesulfonic acid, calcium salt, not more than 0.2 percent. 3-Hydroxy-2-naphthoic acid, not more than 0.4 percent. Subsidiary colors, not more than 4 percent. Total color not less than 85 percent.