Identity. (1) The color additive D&C Blue No. 4 is principally the diammonium salt of ethyl[4-[p[ethyl(m- sulfobenzyl)ami-no]-α-(o- sulfophenyl)benzylidene]-2,5-cyclo-hexadien-1-ylidene] (m- sulfobenzyl) ammonium hydroxide inner salt with smaller amounts of the isomeric diammonium salts of ethyl [4-[p-[ethyl(p- sulfobenzyl) amino]-α-(o- sulfophenyl) benzylidene]-2,5-cyclohexadien - 1-ylidene](p- sulfobenzyl) ammonium hydroxide inner salt and ethyl[4-[p-[ethyl (o- sulfobenzyl)amino]-α-(o- sulfophenyl) benzylidene]-2,5-cyclohexadien-1-ylidene] (o- sulfobenzyl) ammonium hydroxide inner salt.

Color additive mixtures for use in externally applied drugs made with D&C Blue No. 4 may contain only those diluents that are suitable and that are listed in part 73 of this chapter for use in color additive mixtures for coloring externally applied drugs.

Specifications. D&C Blue No. 4 shall conform to the following specifications and shall be free from impurities other than those named to the extent that such impurities may be avoided by good manufacturing practice:

Uses and restrictions. D&C Blue No. 4 may be safely used in externally applied drugs in amounts consistent with good manufacturing practice.

Labeling. The label of the color additive and any mixtures prepared therefrom intended solely or in part for coloring purposes shall conform to the requirements of § 70.25 of this chapter.

Certification. All batches of D&C Blue No. 4 shall be certified in accordance with regulations in part 80 of this chapter.