| 11. | Purpurin fluoresces yellow to red under ultraviolet light, while synthetic alizarin slightly shows violet.
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| 12. | Alizarin was discovered before purpurin, by heating the ground madder with acid and potash.
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| 13. | The main colorant of madder was discovered by Robiquet and Colin in 1827 and called alizarin.
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| 14. | This enzyme is also called "'uridine diphosphoglucose-alizarin glucosyltransferase " '.
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| 15. | Alizarin had been isolated from madder root some forty years earlier in 1826 by the French chemist Pierre Robiquet.
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| 16. | They then found that madder lake contained two colorants, the red alizarin and the more rapidly fading purpurin.
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| 17. | In collaboration with professor Carl Graebe and Carl Liebermann from Berlin University the first synthetic dyestuff alizarin was discovered.
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| 18. | Alizarin changes color depending on the pH of the solution it is in, thereby making it a pH indicator.
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| 19. | Alizarin continues to be used commercially as a red textile dye, but to a lesser extent than 100 years ago.
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| 20. | Analysis of the fibers and dyes revealed the use of alizarin, purpurin, rubiadin, quinizarin, indigo and indirubin.
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