In Zamboni solution, which component provides the fixative that dissociates into formaldehyde when heated?

• A. Paraformaldehyde
• B. Picric acid
• C. Sodium hydroxide
• D. Phosphate buffer

Answer: (A)

Paraformaldehyde is the polymerized form of formaldehyde used in Zamboni fixative as the source of the fixative. When heated, paraformaldehyde depolymerizes, releasing formaldehyde that then cross-links proteins, preserving tissue structure. The other components—picric acid and acetic acid provide additional fixation effects and nuclear detail, while sodium hydroxide or a phosphate buffer simply adjust pH or maintain the solution, not release formaldehyde. Thus, the fixative that dissociates into formaldehyde upon heating is paraformaldehyde.