Title: Alizarin
CAS Registry Number: 72-48-0
CAS Name: 1,2-Dihydroxy-9,10-anthracenedione
Additional Names: 1,2-dihydroxyanthraquinone; C.I. Mordant Red 11; C.I. Pigment Red 83; C.I. 58000
Molecular Formula: C14H8O4
Molecular Weight: 240.21
Percent Composition: C 70.00%, H 3.36%, O 26.64%
Literature References: Occurs in the root of the madder plant (Rubia tinctorum L., Rubiaceae; Krappwurzel) in combination with 2 mols glucose, called ruberythric acid. Was known and used in ancient Egypt, Persia, and India. Synthesized from 2-anthraquinonesulfonic acid sodium salt : Caro et al., Ber. 3, 359 (1870); Perkin, Ber. 9, 281 (1876). Historical review: Fieser, J. Chem. Educ. 7, 2609 (1930). Laboratory prepn: Gattermann-Wieland, Laboratory Methods of Organic Chemistry (New York, 1937). Modern methods of manufacture: Pohl, Ullmanns Encyklopädie der technischen Chemie vol. I, p 200; Fierz-David and Blangey, Grundlegende Operationen der Farbenchemie (Vienna, 5th ed., 1943). See also Colour Index vol. 4, (3rd ed., 1971) p 4513.
Properties: Orthorhombic, orange needles by sublimation or from abs alc. Solvated scales from dil alc or by evaporation from ether. Sublimes at 110° (2 mm Hg). mp 290°. bp 430°. Absorption spectrum: Moir, J. Chem. Soc. 1927, 1810. Soly in water at 18°: 2.1´10-6 mols/l; at 25°: 2.5´10-6 mols/l. Sol in 300 parts boiling water; moderately sol in alcohol, freely in hot methanol and in ether at 25°. Also sol in benzene, toluene, xylene, pyridine, carbon disulfide, glacial acetic acid. Sol in water solns of alkalies with blue color, but without fluorescence. Fluorescent solns indicate unchanged 2-anthraquinone sodium sulfonate.
Melting point: mp 290°
Boiling point: bp 430°
Derivative Type: 1-Methyl ether
Molecular Formula: C15H10O4
Molecular Weight: 254.24
Percent Composition: C 70.86%, H 3.96%, O 25.17%
Properties: Orange needles with 1H2O from dil methanol. When dried at 100° mp 179°.
Melting point: mp 179°
Derivative Type: 2-Methyl ether
Molecular Formula: C15H10O4
Molecular Weight: 254.24
Percent Composition: C 70.86%, H 3.96%, O 25.17%
Properties: Orange needles from alcohol, mp 231°.
Melting point: mp 231°
Derivative Type: Dimethyl ether
Molecular Formula: C16H12O4
Molecular Weight: 268.26
Percent Composition: C 71.64%, H 4.51%, O 23.86%
Properties: Golden-yellow needles from alcohol, mp 215°.
Melting point: mp 215°
Use: In the manufacture of acid and chrome dyes for wool; acid-base indicator (in 0.5% alcoholic soln; pH: yellow 5.5, red 6.8); in spot tests as reagent for aluminum, indium, mercury, zinc, and zirconium; biological stain.
Alizarin Cyanine Green F Alizarine Blue Alizarine Orange Alizarine Yellow R Alkanet

Skeletal formula of alizarin
Ball-and-stick model of alizarin
Sample of alizarin
CAS number 72-48-0 YesY
PubChem 6293
ChemSpider 6056 YesY
KEGG C01474 YesY
ChEBI CHEBI:16866 YesY
Jmol-3D images Image 1
Molecular formula C14H8O4
Molar mass 240.21 g mol−1
Appearance orange-red crystals or powder
Density 1.540 g/cm3
Melting point 279–83 °C
Boiling point 430 °C
Solubility in water slightly to sparingly soluble
Acidity (pKa) 6.94
MSDS External MSDS
R-phrases R36 R37 R38
S-phrases S26 S36
Related compounds
Related compounds anthraquinone, anthracene
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Alizarin or 1,2-dihydroxyanthraquinone (also known as Mordant Red 11 and Turkey Red[1]) is an organic compound with formula C
that has been used throughout history as a prominent red dye, principally for dyeing textile fabrics. Historically it was derived from the roots of plants of the madder genus.[2] In 1869, it became the first natural pigment to be duplicated synthetically.[3]

Alizarin is the main ingredient for the manufacture of the madder lake pigments known to painters as Rose madder and Alizarin crimson. Alizarin in the most common usage of the term has a deep red color, but the term is also part of the name for several related non-red dyes, such as Alizarine Cyanine Green and Alizarine Brilliant Blue. A notable use of alizarin in modern times is as a staining agent in biological research because it stains free calcium and certain calcium compounds a red or light purple color. Alizarin continues to be used commercially as a red textile dye, but to a lesser extent than 100 years ago.