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