Alizarine

Anlhraquinone-2-su phonic acid. The sodium salt, commonly called silver salt , is used for the preparation of alizarin and 2-aminoanthraquinone and to prepare Fieser s solution. Aminoanthraquinone derivatives are the basis of many dyestuffs. 

Addition of ammonium hydroxide to an aluminium salt in solution in presence of alizarin, gives a pink precipitate. 

The way a synthesis is planned has changed substantially over time. Until the beginning of the 20th century many noteworthy syntheses had been developed, c.g., of alizarin (C. Gracbc, C, Licbermann, 1869) and indigo (A, Bacycr, 1878). 

Anthraquinone is of great technical importance, as many of its derivatives form valuable dyes notable among these are the hydroxy-derivatives (alizarin, etc.)y the amino-derivatives (indanthrene, etc.) and the sulphonic acids. 

Benzoquinone, p-toluquinone, 1 2-naphthoquinone,, naphthoquinone, anthraquinone,, io-phenanthraquinone, alizarin. 

Anthraquinone and alizarin are unaffected by sulphurous acid. Phenanthraquinone is reduced in warm ethanolic solution by SO2 water to hydrophenanthraquinone, m.p. 147°. 1,2-Naphthoquinone gives the corresponding hydronaphthoquinone, m.p. 60°. Toluquinone gives toluhydroquinone, m.p. 124 . 

Alizarin dissolves in aqueous NaOH solution giving a purple solu tion. Calcium hydroxide will precipitate a blue sdt from this solution. Anthraquinone is unaffected by NaOH solution. 

Alizarin. Dissolve successively in 75 ml. of water 6 g. of potassium chlorate, 20 g. of sodium anthraquinone- p-sulphonate and 75 g. of sodium hydroxide. Transfer the mixture to a 500 ml. autoclave (compare Section VI,4) and heat for 20 hours at 170°. After coohng, scrape out... 

Plane one drop of the solution upon zireonium-alizarin-S test paper. A yellow eolour on the red paper indicates the presenee of fluoride. 

Quinones that are based on the anthracene ring system are called anthraqumones Alizarin is one example of an anthraqumone dye... 

Qumones are colored p benzoqumone for example is yellow Many occur natu rally and have been used as dyes Alizarin is a red pigment extracted from the roots of the madder plant Its preparation from anthracene a coal tar derivative m 1868 was a significant step m the development of the synthetic dyestuff industry... 

Alizarin, dihydroxyanthraquinone (indicator) dissolve 0.1 g in 100 mL alcohol pH range yellow 5.5-6.8 red. 

Indicator solutions a number of indicator solutions are listed in this section under the names of the indicators e.g., alizarin, aurin, azolitmin, et al., which follow alphabetically. See also various index entries. 

Rosolic acid, aurin, corallin, corallinphthalein, 4,4 -dihydroxy-fuchsone, 4,4 -dihydroxy-3-methyl-fuchsone (indicator) dissolve 0.5 g in 50 mL alcohol and dilute with water to 100 mL. Salicyl yellow (indicator) see alizarin yellow GG. 

Structure of (a) alizarin garnet R, and (b) its metal-ligand complex with AP+. 

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