Alizarin (also known as 1,2-dihydroxyanthraquinone, Mordant Red 11, C.I. 58000, and Turkey Red[ SigmaAldrich Catalog: Alizarin]) is an organic compound with formula that has been used throughout history as a red dye, principally for dyeing textile fabrics. Historically it was derived from the roots of plants of the Rubia genus.[The primary madder species from which alizarin historically has been obtained is Rubia tinctorum. See also ] In 1869, it became the first natural dye to be produced synthetically.[
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Alizarin is the main ingredient for the manufacture of the madder Lake pigment known to painters as rose madder and alizarin crimson. Alizarin in the most common usage of the term has a deep red color, but the term is also part of the name for several related non-red dyes, such as Alizarine Cyanine Green and Alizarine Brilliant Blue. A use of alizarin in modern times is as a staining agent in biological research because it stains free calcium and certain calcium compounds a red or light purple color. Alizarin continues to be used commercially as a red textile dye, but to a lesser extent than in the past.
History
Madder has been cultivated as a natural dye since antiquity in central Asia and Egypt, where it was grown as early as 1500 BC. Cloth dyed with madder root pigment was found in the tomb of the Pharaoh Tutankhamun,[Many examples of the use of the word "madder", meaning the roots of the plant Rubia tinctorum used as a dye, are given in the Middle English Dictionary, a dictionary of late medieval English.] In 17th century England, alizarin was used as a red dye for the clothing of the parliamentary New Model Army. The distinctive red color would continue to be worn for centuries (though also produced by other dyes such as cochineal), giving English and later British soldiers the nickname of "redcoats".
The madder dyestuff is combined with a dye mordant. Depending on which mordant is used, the resulting color may be anywhere from pink through purple to dark brown. In the 18th century, the most valued color was a bright red known as "Turkey Red". The combination of mordants and overall technique used to obtain the Turkey Red originated in the Middle East or Turkey (hence the name). It was a complex and multi-step technique in its Middle Eastern formulation, some parts of which were unnecessary.[ Additional 18th century history at ] The process was simplified in late 18th-century Europe. By 1804, dye maker George Field in Britain had refined a technique to make Lake pigment madder by treating it with alum, and an alkali,[George Field's notes are held at the Courtauld Institute of Art. See ] that converts the water-soluble madder extract into a solid, insoluble pigment. This resulting madder lake has a longer-lasting color, and can be used more efficaciously, for example by blending it into a paint. Over the following years, it was found that other metal salts, including those containing iron, tin, and chromium, could be used in place of alum to give madder-based pigments of various other colors. This general method of preparing lakes has been known for centuries
In 1826, the France chemist Pierre-Jean Robiquet found that madder root contained two colorants, the red alizarin and the more rapidly fading purpurin.[See:
] The alizarin component became the first natural dye to be synthetically duplicated in 1868 when the Germany chemists Carl Graebe and Carl Liebermann, working for BASF, found a way to produce it from anthracene.[Note:
In 1868, Graebe and Liebermann showed that alizarin can be converted into anthracene. See: C. Graebe and C. Liebermann (1868) "Ueber Alizarin, und Anthracen" (On alizarin and anthracene), Berichte der Deutschen chemischen Gesellschaft zu Berlin, 1 : 49–51.
In 1869, Graebe and Liebermann announced that they had succeeded in transforming anthracene into alizarin. See: C. Graebe and C. Liebermann (1869) "Ueber künstliche Bildung von Alizarin" (On the artificial formation of alizarin), Berichte der Deutschen chemischen Gesellschaft zu Berlin, 2 : 14.
For Graebe and Liebermann's original process for making alizarin from anthracene, see: Charles Graebe and Charles Liebermann, "Improved process of preparing alizarine," U.S. Patent no. 95,465 (issued: October 5, 1869). (See also their English patent, no. 3,850, issued December 18, 1868.)
A more efficient process for making alizarin from anthracene was developed by Caro, Graebe and Liebermann in 1870. See: H. Caro, C. Graebe, and C. Liebermann (1870) "Ueber Fabrikation von künstlichem Alizarin" (On the manufacture of artificial alizarin), Berichte der Deutschen chemischen Gesellschaft zu Berlin, 3 : 359–360.] The Bayer AG company draws its roots from alizarin as well.
The synthetic alizarin could be produced for a fraction of the cost of the natural product, and the market for madder collapsed virtually overnight. The principal synthesis entailed bromination of anthraquinone by bromine (in a sealed tube at 100 oC) to give 1,2-dibromoanthraquinone. Then the two bromine atoms were substituted by -OH by heating (170 oC) with KOH, followed by treatment with strong acid.
Alizarin, as a dye, has been largely replaced today by the more light-resistant quinacridone pigments developed at DuPont in 1958.
Structure and properties
Alizarin is one of ten dihydroxyanthraquinone isomers. It is soluble in hexane and chloroform, and can be obtained from the latter as red-purple crystals, melting point 277–278 °C.[
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Alizarin changes color depending on the pH of the solution it is in, thereby making it a pH indicator.
Applications
Alizarin Red is used in a biochemical assay to determine, quantitatively by colorimetry, the presence of calcific deposition by cells of an Ossification lineage. As such it is an early stage marker (days 10–16 of in vitro culture) of matrix mineralization, a crucial step towards the formation of calcified extracellular matrix associated with true bone.
Alizarin's abilities as a biological stain were first noted in 1567, when it was observed that when fed to animals, it stained their teeth and bones red. The chemical is now commonly used in medical studies involving calcium. Free (ionic) calcium forms precipitates with alizarin, and tissue block containing calcium stain red immediately when immersed in alizarin. Thus, both pure calcium and calcium in bones and other tissues can be stained. These alizarin-stained elements can be better visualized under fluorescent lights, excited by 440–460 nm.
In clinical practice, it is used to stain synovial fluid to assess for basic calcium phosphate crystals.[
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In geology, it is used as a stain to differentiate the calcium carbonate minerals, especially calcite and aragonite in thin section or polished surfaces.
Madder lake had been in use as a red pigment in paintings since antiquity.[Schweppe, H., and Winter, J. Madder and Alizarin in Artists’ Pigments. A Handbook of Their History and Characteristics, Vol 3: E.W. Fitzhugh (Ed.) Oxford University Press 1997, p. 111 – 112]
File:Red alizarin 1.jpg|Red alizarin staining of rat's embryonic bones for osteogenesis study
File:N pectoralis.jpg|Red alizarin stained juvenile Roosterfish lit by fluorescent light.
See also
Further reading
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Schweppe, H., and Winter, J. "Madder and Alizarin", in Artists’ Pigments: A Handbook of Their History and Characteristics, Vol. 3: E.W. Fitzhugh (Ed.) Oxford University Press 1997, pp. 109–142
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