Chrysoine resorcinol is a synthetic azo dye which was formerly used as a food additive. In Europe, it was banned as a food additive in 1977. In the US, it was banned in 1988.
Chrysoine resorcinol can be used as a pH indicator with a color change between pH 11 and pH 12.7.
| Chrysoine resorcinol (pH indicator) | ||
| below pH 11.0 | above pH 12.7 | |
| 11.0 | ↔ | 12.7 |
In colorimetry it has an absorption maximum of 387 nm.