Mercuric salts produce which pigment in tissue?

• A. Brownish-black pigment
• B. Yellow pigment
• C. Purple pigment
• D. Green pigment

Answer: (A)

Mercuric salts leave a dark, stable pigment in tissue because mercury ions react with sulfur-containing compounds in the tissue to form mercuric sulfide, which is insoluble and appears brownish-black under the microscope. This pigment is a characteristic artifact of fixation with mercuric chloride and tends to persist through processing, often seen as granular deposits within cells or the surrounding matrix. It’s distinctly dark, unlike yellow or green endogenous pigments or the purple hue from certain stains, which helps explain why the correct color match is brownish-black.