Nuclear staining is made more selective by adding what to the hematoxylin solution?

• A. Acetic acid
• B. Sodium chloride
• C. Glycerol
• D. Ethanol

Answer: (A)

Adding acetic acid to hematoxylin makes the staining solution more acidic, which heightens the affinity of the hematein–mordant complex for nuclear material (primarily DNA and RNA) and reduces non-specific uptake by cytoplasmic components. This results in crisper, more selective nuclear staining. The acetic acid also helps stabilize the dye complex and aids differentiation, preventing overstaining of other tissue elements. The other substances—sodium chloride, glycerol, and ethanol—do not provide this targeted effect on nuclear selectivity; they mainly alter ionic strength, humectancy, or dehydration without improving nuclear specificity.