Which chemical is used to ripen hematoxylin solutions?

• A. Ferric chloride
• B. Ammonium aluminum sulfate
• C. Sodium chloride
• D. Acetic acid

Answer: (A)

Ripening hematoxylin means oxidizing the dye to its active form, hematein, so it can form the stable, staining complex with a mordant and clearly color nuclei. Ferric chloride provides mild oxidation and supplies ferric ions that help convert hematoxylin to hematein and enable the dye-mordant complex that gives a crisp bluish-black nuclear stain. The other substances don’t oxidize hematoxylin: ammonium aluminum sulfate acts mainly as a mordant, while sodium chloride and acetic acid adjust ionic strength and pH, respectively, but don’t ripen the dye.