A painted swatch of Madder lake (Alizarin):
About the chemical structure:
| Chemical name: | 1,2-dihydroxyantraquinone |
| Formula: |  |
| 3D model: |
grey = carbon, red = oxygen, white = hydrogen |
| Refractive index: | Madder lake: 1.66; alizarin: 1.70 |
How can you identify Madder lake (Alizarin)?
Chemical identification:
The base on which both varieties are substrated is indistinguishable under the microscope. Nor can the natural and artificial be identified even at high magnification. They are both soluble in hydrochloric acid
Spectra:
Raman spectra: Madder lake (pdf file download; at University of Florence, Italy)
Mass spectra: alizarin (at: Integrated Spectral Data Base System for Organic Compounds, Japan)
IR spectra: alizarin (at: Integrated Spectral Data Base System for Organic Compounds, Japan)
Usage and handling:
| Permanence: | Toxicity: |
|---|---|
| outstanding lightfastness | MSDS (at Fisher Scientific) |
Literature:
Artists’ Pigments. A Handbook of Their History and Characteristics, Vol 3: E.W. Fitzhugh (Ed.) Oxford University Press 1997, p. 109 - 142.
Stössel, I., Rote Farblacke in der Malerei - Herstellung und Verwendung im deutschsprachigen Raum zwischen ca. 1400-1850, Publikationsreihe des Instituts für Malerei Stuttgart, 1985
Koch, H. M. und Pfeifer, P., Naturfarbstoffe im Unterricht. Antrachinonfarbstoffe der Krappwurzel. Praxis der Naturw.-Chemie, 10, 1999, s. 25-29
Krapplack (at Pigmentlexikon by Th. Seilnacht)
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