What is the name of the pure polymer form of formaldehyde?

• A. Paraformaldehyde.
• B. Formalin.
• C. Glutaraldehyde.
• D. Picric acid-formaldehyde.

Answer: (A)

Paraformaldehyde is the solid, polymeric form of formaldehyde. It consists of repeating –CH2–O– units linked together into a chain, making a pure polymer. When it’s heated or dissolved in water, it depolymerizes back to formaldehyde gas or formaldehyde in solution, which is the form that fixes tissues. Formalin, by contrast, is formaldehyde dissolved in water, so it’s not the polymer form. Glutaraldehyde is a different chemical (a five-carbon dialdehyde) used for fixation, not the polymer of formaldehyde. Picric acid-formaldehyde isn’t a standard polymer form. So the pure polymer form is paraformaldehyde.