- alizarin
- 1,2-Dihydroxyanthraquinone; a red dye that occurs in the root of madder (Rubia tinctorum and other Rubiaceae) in glucose combination (ruberythric acid) as orange needles, slightly soluble in water; used by the ancients as a dye. Now made synthetically from anthracene and used in the manufacture of dyes, e.g., a. blue, a. orange, “Turkey red.” As an indicator, it is yellow below pH 5.5 and red above pH 6.8; other modified alizarins have other colors and change color at other pH values.- a. cyanin [C.I. 58610] disulfonate of hexahydroxyanthraquinone; an acid dye used as a nuclear stain after mordanting and as a fluorochrome in ultraviolet microscopy.- a. red S [C.I. 58005] sodium a. sulfonate; used as a stain for calcium in bone (calcium appears red-orange, magnesium, aluminum, and barium are varying shades of red), in the determination of fluorine; as a pH indicator it changes from yellow to purple between pH 3.7 and 5.2.
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1) an orange or red crystalline compound C14H8O4 formerly prepared from madder and now made synthetically from anthraquinone that was formerly used in dyeing but is now used more in making red pigments2) any of a group of dyes that are similar to alizarin in dyeing properties or derivation* * *
n.an orange-red dye derived from coal tar and originally isolated from the plant madder (Rubia tinctorum). Alizarin is insoluble in water but dissolves in alkalis, alcohol, and ether. It is used as a pH indicator and as a histochemical reagent for calcium, thallium, titanium, and zirconium.* * *
aliz·a·rin (ə-lizґə-rin) [Ar. ala sara extract] a red crystalline dye, prepared synthetically or obtained from madder; its compounds are used as indicators.
Medical dictionary. 2011.
