Zinc is a satisfactory replacement for mercury in some fixative solutions.

• A. True
• B. False
• C. Only for light microscopy
• D. Never used

Answer: (A)

Zinc-based fixatives can replace mercuric fixatives because zinc forms cross-links with tissue proteins in a way that preserves morphology, while offering much lower toxicity. A common example is zinc formalin, which combines zinc salts with formaldehyde in a buffered solution. It provides good preservation of tissue architecture and nuclear detail and tends to maintain antigenicity better for immunohistochemistry, making it versatile for routine light microscopy and various stains. Although mercuric fixatives historically gave excellent nuclear preservation, their safety risks drive the shift to zinc formulations, which deliver comparable results with safer handling. In practice, most tissues and standard stains work well with zinc fixatives, though some situations may require optimization.