Which chemical is used in the prep of Harris hematoxylin?

• A. Ferric chloride
• B. Ammonium aluminum sulfate
• C. Sodium bicarbonate
• D. Glacial acetic acid

Answer: (B)

Staining nuclei with hematoxylin relies on forming a stable complex with a mordant so the dye remains anchored in tissue. Harris hematoxylin uses an aluminum-based mordant, specifically ammonium aluminum sulfate, to convert hematoxylin to hematein and to form the insoluble hematein–aluminum complex that binds to nuclear components. This complex endures through processing and gives the characteristic blue-black nuclear stain. Ferric chloride would introduce iron and is associated with different formulations; sodium bicarbonate and glacial acetic acid are used mainly for pH adjustment or buffering, not as the mordant in Harris hematoxylin.