Aurin


 * ''For the French commune, see Aurin, Haute-Garonne.
 * ''For the Aragonese village, see Aurin, Sabiñánigo, Huesca, España.

Aurin (C.I. 43800), sometimes named rosolic acid or corallin, chemically 4-[bis(p-hydroxyphenyl)methylene]-2,5-cyclohexadien-1-one, is an organic compound, forming yellowish or deep-red crystals with greenish metallic luster. It is practically insoluble in water, freely soluble in alcohol. It is soluble in strong acids to form yellow solution, or in aqueous alkalis to form carmine red solutions. Due to this behaviour it can be used as pH indicator with pH transition range 5.0 - 6.8. It used as intermediate in manufacturing of dyes.