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Alizarin is an organic compound that is historically important as a prominent dye. It is an anthraquinone originally derived from the root of the madder plant. In 1869, it became the first natural pigment to be duplicated synthetically. Alizarin is also the name for a variety of related dyes, such as "Alizarine Cyanine Green G" and "Alizarine Brilliant Blue R." Can also be used to identify the color "Alizarin Crimson". The word alizarin derives from the Arabic al-usara, juice.

Alizarin was used as a red die for the English parliamentary "new model" army. The distinctive red color would continue to be worn for centuries, giving English and later British soldiers the nickname of "redcoat".

History

Madder has been cultivated as a dyestuff since antiquity in central Asia and Egyptmarker, where it was grown as early as 1500 BC. Cloth dyed with madder root pigment was found in the tomb of the Pharaoh Tutankhamun and in the ruins of Pompeiimarker and ancient Corinthmarker. In the Middle Ages, Charlemagne encouraged madder cultivation. It grew well in the sandy soils of the Netherlandsmarker and became an important part of the local economy.

By 1804, the Englishmarker dye maker George Field had refined the technique to lake madder by treating it with alum, and an alkali, 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 Frenchmarker chemist Pierre-Jean Robiquet found that madder root contained two colorants, the red alizarin and the more rapidly fading purpurin. The alizarin component became the first natural dye to be synthetically duplicated in 1868 when the Germanmarker chemists Carl Graebe and Carl Liebermann, working for BASFmarker, found a way to produce it from anthracene. About the same time, the Englishmarker dye chemist William Henry Perkin independently discovered the same synthesis, although the BASF group filed their patent before Perkin by only one day.

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 oxidation of anthraquinone-2-sulfonic acid with sodium nitrate in concentrated sodium hydroxide. Alizarin itself has been in turn largely replaced today by the more light-resistant quinacridone pigments developed at DuPont in 1958.

Applications – Alizarin Red

Alizarin red is used in a biochemical assay to determine, quantitatively by colorimetry, the presence of calcific deposition by cells of an osteogenic lineage. As such it is an early stage marker (days 10–16 of in vitro culture) of matrix mineralisation, a crucial step towards the formation of calcified extracellular matrix associated with true bone.

In clinical practice it is also used to stain synovial fluid to assess for basic calcium phosphate crystals.

Alizarin Crimson

Alizarin Crimson can also be identified as "Alizarin".At right is displayed the color alizarin crimson.

Alizarin crimson in human culture

Music



  • Alizarin crimson is mentioned in Karlheinz Stockhausen's 1966/67 musical composition Hymnen, where it is included in a spoken fugue where the names of dozens of different shades of red are intermingled as a symbol of the various forms of Communism that existed at that time.


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