What is "paraformaldehyde"

paraformaldehyde \par`a*form*al"de*hyde\, n. [Pref. para- + formaldehyde.] (Chem.) A polymer of formaldehyde obtained as a white crystalline substance by concentration of a formaldehyde solution. Formula (CH20)n. It dissolves in hot water with the release of formaldehyde, and is used as a disinfectant.

n. (context organic compound English) A solid oligomer of formaldehyde that is used as a fumigant, and as a fixative in histology

Paraformaldehyde (PFA) is the smallest polyoxymethylene, the polymerization product of formaldehyde with a typical degree of polymerization of 8–100 units. Paraformaldehyde commonly has a slight odor of formaldehyde due to decomposition. Paraformaldehyde is a poly- acetal.