Paraformaldehyde ( Paraform (molecular formula ho - (ch2O) n-h, where n is the degree of polymerization, with an n-value range from 8 to 100), also known as polyformaldehyde, polyformaldehyde, acetal, or solid formaldehyde, is a white amorphous particle or powder with a formaldehyde odor, and is a linear polymer of formaldehyde.

Polyformaldehyde has no fixed melting point and decomposes upon heating. It has a melting point of 120-170 ℃ and is easily soluble in hot water, releasing formaldehyde. It is slowly soluble in cold water and can dissolve in caustic soda and alkali metal carbonate solutions. It is insoluble in alcohols and ethers, and highly polymer insoluble in water. Reactions similar to formaldehyde can occur, such as chloromethylation and the formation of acetals with alcohols. Used for synthesizing resins, adhesives, pharmaceuticals, fungicides, insecticides, disinfectants, etc.