Aurin (C.I. 43800), sometimes named rosolic acid or corallin is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon- hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...

, forming

yellow Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In ...

ish or deep-red crystals with

green Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 Nanometre, nm. In subtractive color systems, used in painting and color printing, it is created by ...

ish 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 is used as an intermediate in manufacturing of dyes.

Synthesis

Aurin was first prepared in 1834 by the German chemist Friedlieb Ferdinand Runge, who obtained it by distilling coal tar. He named it ''Rosölsäure'' or ''Rosaölsäure'' (red oil acid). In 1861, the German chemists Hermann Kolbe and Rudolf Schmitt presented the synthesis of aurin by heating oxalic acid and creosote (which contains phenol) in the presence of concentrated sulfuric acid. (Gradually, chemists realized that commercial aurin was not a pure compound, but was actually a mixture of similar compounds.) Aurin is formed by heating of phenol and oxalic acid in concentrated sulfuric acid. : Aurinsynthese

Safety

Aurin may cause eye, skin, and respiratory tract irritation. Ingestion and inhalation should be avoided. Aurin was reported to have endocrine disruptor chemical (EDC) properties.

References

External links

MSDS at Oxford UniversityHistory of aurin in ''Heinrich Caro and the creation of modern chemical industry''
*{{Cite NIE, wstitle=Aurin, short=x Triarylmethane dyes PH indicators Phenol dyes Bis(4-hydroxyphenyl)methanes