Aurin Explained

Aurin (C.I. 43800), sometimes named rosolic acid or corallin 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 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).^{[1] [2]} 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.^[3] (Gradually, chemists realized that commercial aurin was not a pure compound, but was actually a mixture of similar compounds.^{[4] [5]})

Aurin is formed by heating of phenol and oxalic acid in concentrated sulfuric acid.

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.^[6]

External links

• MSDS at Oxford University
• History of aurin in Heinrich Caro and the creation of modern chemical industry
• Aurin. x.

Notes and References

1. Runge. F. F.. Ueber einige Produkte der Steinkohlendestillation. Annalen der Physik und Chemie. 1834. 31. 5 . 65–78. 10.1002/andp.18341070502 . 1834AnP...107...65R . On some products of coal tar distillation. German. ; see p. 70.
2. In 1859, the German-English chemist Hugo Müller (de) (1833–1915) found that rosolic acid could be produced simply by mixing phenol and calcium carbonate and then exposing the mixture to air for a prolonged time. Müller. Hugo. Note on rosolic acid. Quarterly Journal of the Chemical Society. 1859. 11. 1. 1–5. 10.1039/QJ8591100001.
3. Kolbe. H.. Schmitt. R.. Rother Farbstoff aus dem Kreosot. Annalen der Chemie. 1861. 119. 169–172. Red dye from creosote. German.
4. See the papers of the English chemist Richard S. Dale and the German-English chemist Carl Schorlemmer and of the German chemist Heinrich Fresenius (de) (1847–1920).
   • Dale. R.S.. Schorlemmer. C.. On aurin. Journal of the Chemical Society. 1871. 24. 466–467. 10.1039/JS8712400466.
   • Dale. R.S.. Schorlemmer. C.. On aurin. Journal of the Chemical Society. 1872. 25. 74–75.
   • Dale. R.S.. Schorlemmer. C.. On aurin. Journal of the Chemical Society. 1873. 26. 434–444. 10.1039/JS8732600434.
   • Dale. R.S.. Schorlemmer. C.. On aurin, part II. Journal of the Chemical Society. 1879. 35. 148–159. 10.1039/CT8793500148.
   • Fresenius. H.. Ueber Rosolsäure. Journal für praktische Chemie. 1871. 3. 477–480. 2nd series. 10.1002/prac.18710030149. On rosolic acid. German.
   • A review of findings about aurin up to 1872 appeared in: Fresenius. H.. Ueber das Corallin. Journal für praktische Chemie. 1872. 5. 4. 184–191. 2nd series. 10.1002/prac.18720050117. On corallin. German.
   • Fresenius. H.. Corallin. Journal of the Chemical Society. 1872. 25. 705–706.
5. Thorpe, Thomas Edward, ed., A Dictionary of Applied Chemistry, 2nd ed. (London, England: Longmans, Green, and Co., 1913), vol. 5, "Triphenylmethane colouring matters," p. 551. From p. 551: "The researches of Dale and Schorlemmer, Zulkowski, and others have shown that common aurin consists of a mixture of a number of substances, which, in a pure state, are well crystallised."
6. ((Blair, R. M.)) . Toxicological Sciences . The Estrogen Receptor Relative Binding Affinities of 188 Natural and Xenochemicals: Structural Diversity of Ligands . 54 . 1 . 138–153 . 1 March 2000 . 1096-0929 . 10.1093/toxsci/54.1.138. 10746941 . free .