Chrysoine resorcinol is a synthetic azo dye which was formerly used as a food additive.[citation needed] In Europe, it was banned as a food additive in 1977.[1] In the US, it was banned in 1988.[2]
Chrysoine resorcinol can be used as a pH indicator with a color change between pH 11 and pH 12.7. In colorimetry, it has an absorption maximum of 387 nm.
Acid orange 6 can be synthesised via the azo coupling of sulfanilic acid and resorcinol,