Fixation with potassium dichromate increases tissue receptivity to which stain?

• A. Eosin
• B. Hematoxylin
• C. PAS
• D. Silver stain

Answer: (A)

Potassium dichromate is a chromic acid fixative that denatures and crosslinks tissue proteins, changing their chemical properties so that basic, positively charged sites become more available to bind. Eosin is an acidic dye that binds to those basic tissue components, giving the cytoplasm and other eosinophilic structures a strong pink coloration. Because this fixative enhances the tissue’s affinity for eosin, staining with eosin becomes more intense and uniform. Other stains rely on different chemical interactions that aren’t specifically amplified by potassium dichromate fixation, so the fixation increases receptivity most notably to eosin.