ironhematoxylin

Iron hematoxylin is a nuclear stain used in histology and light microscopy. It refers to hematoxylin that has been mordanted with iron ions to form a ferric-hematoxylin complex. This complex binds strongly to nucleic acids, producing a deep blue to blue‑black stain of cell nuclei. The resulting staining is more stable and resistant to fading or decolorization than some aluminum-mordanted hematoxylin formulations.

A common variant is Weigert's iron hematoxylin, which uses ferric ions as the mordant and requires an oxidation step to develop the stain, often followed by a differentiation step to adjust intensity. When used in routine practice, iron hematoxylin is typically employed as the primary nuclear stain in paraffin sections, frequently in combination with a counterstain such as eosin or other dyes. The technique yields high-contrast nuclei and is valued for its durability during subsequent histochemical procedures and differentiations.

Chemically, hematoxylin is first oxidized to an active form (hematein) that forms a complex with ferric ions. This complex binds preferentially to acidic components of chromatin, giving clear nuclear delineation. The exact shade and intensity can be influenced by oxidation status, mordant concentration, pH, and the follow-up staining steps.

History and use vary by protocol, with iron hematoxylin favored for its permanence in many staining schemes and its compatibility with multiple counterstains. Alternatives include aluminum-hematoxylin formulations, which produce slightly different nuclear hues and aging characteristics. See also hematoxylin, ferric mordants, and related histology staining methods.