What chemicals serve as mordants in hematoxylin solutions?

• A. Ammonium aluminum sulfate and ferric chloride
• B. Sodium iodate
• C. Methyl green
• D. Ferric chloride

Answer: (A)

Mordants are metal salts that form a hematein-metal complex, which makes hematoxylin bind strongly to nuclear material. In hematoxylin solutions, two common mordants are ammonium aluminum sulfate and ferric chloride. The aluminum salt creates an aluminum-hematein complex that adheres to nuclei, while ferric chloride forms an iron-hematein complex used in iron hematoxylin formulations. Sodium iodate is not a mordant; it oxidizes hematoxylin to hematein. Methyl green is a separate dye used as a counterstain, not a mordant. Because hematoxylin can be used with either mordant, and many formulations rely on one or the other (or specify both as options), the combination of ammonium aluminum sulfate and ferric chloride best represents the chemicals that serve as mordants in hematoxylin solutions.