Among fixatives, which ones contain mercuric chloride and potassium dichromate?

• A. Zenker and Helly
• B. Bouin and Carnoy
• C. Carnoy and Bouin
• D. Formalin and Glutaraldehyde

Answer: (A)

Mercury-containing fixatives use mercuric chloride and potassium dichromate to precipitate and stabilize tissue proteins, giving excellent nuclear detail but requiring careful handling due to toxicity. Zenker’s fixative is built around both of these reagents, making it one of the classic heavy-metal fixatives. Helly’s fixative, used similarly in practice, also includes mercuric chloride and potassium dichromate, providing comparable preservation. The other fixatives listed rely on organic solvents, acids, or aldehydes and do not contain these heavy-metal components: Bouin’s uses picric acid, formaldehyde, and acetic acid; Carnoy’s uses ethanol, chloroform, and acetic acid; and formalin with glutaraldehyde are aldehyde fixatives without mercuric chloride or potassium dichromate.