Which type of metal salt serves as the mordant in Weigerts hematoxylin?

• A. Iron
• B. Aluminum
• C. Copper
• D. Manganese

Answer: (A)

The key idea is how a mordant works in hematoxylin staining. A mordant forms a complex with the oxidized form of the dye (hematein) so it can bind tightly to tissue components, especially nuclei, producing a stable stain. Weigert’s hematoxylin uses an iron mordant—typically ferric iron from ferric ammonium sulfate—to create an iron-hematein complex that yields a dark blue-black nuclear stain. This iron mordant differentiates it from other hematoxylin formulations that use aluminum mordants (which tend to give a different, usually lighter blue nuclear color). Copper and manganese aren’t used as the standard mordants for Weigert’s hematoxylin. So iron is the correct mordant for this stain.