A blue dye obtained from the leguminous tree logwood (Haematoxylon campechianum) that stains nuclei and cellulose cell walls blue. Haematoxylin itself is not a stain until it has been oxidized to haematin. It also usually requires a mordant, such as iron alum or an aluminium salt. Different haematoxylin solutions can be prepared, e.g. Delafield's haematoxylin, which can be used as a counterstain with safranin. See also staining.
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