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A red crystalline component that is the coloring agent in logwood dye. Logwood dye, or hematoxylon, is contained in the heartwood of the tree. The blood red extract is obtained by boiling the chips in water. It contains about 10% of the colorant hematoxylin along with resins and tannins. Hematoxylin oxidizes to form the reddish-brown metallic crystals of hematein that are insoluble in water. Using a variety of mordants, the extract can be prepared as a lake ranging in color from red to brown to navy (chrome), violet (alum) to black (iron). Logwood was used in black inks (iron gall ink and bichromate ink) and watercolors. It is still used to dye textiles and leather black. Hematoxylin is also used as a histological stain in the preparation of organic tissues for microscopic examination.

Synonyms and Related Terms

logwood dye; Natural Black I; CI 75290; haematoxylin (Br.); hematoxilina (Esp., Port.); hydroxybrasilin; hematoxylon; haematin; hematin

Chemical structure


Other Properties

Soluble in hot water, ethanol, glycerol and alkali hydroxides.

Composition C10H14O6-3H2O
CAS 517-28-2
Melting Point 100-120
Molecular Weight mol. wt. = 302.28

Hazards and Safety

May be carcinogenic. Contact may cause irritation.

Mallinckrodt Baker: MSDS

Sources Checked for Data in Record

  • Helmut Schweppe, Schweppe color collection index and information book
  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 4671
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
  • Website address 1 Comment: www.hants.org.uk/museums - conservation termlist
  • Colour Index International online at www.colour-index.org

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