Paraformaldehyde 3209372 214736674 2008-05-25T01:19:38Z Cacycle 83784 Synthesis, used as {{Chembox new | ImageFile = Paraformaldehyd.svg | ImageSize = 150px | IUPACName = Polyoxymethylene | OtherNames = | Section1 = {{Chembox Identifiers | CASNo = 30525-89-4 | PubChem = 24898648 | SMILES = }} | Section2 = {{Chembox Properties | Formula = (CH<sub>2</sub>O)<sub>n</sub> (n = 8 - 100) | MolarMass = | Appearance = white crystalline solid | Density = 0.88 g·cm<sup>−3</sup> (20 ºC) | MeltingPt = 120-170 °C | BoilingPt = | Solubility = low}} | Section3 = {{Chembox Hazards | EUClass = Toxic (T); Corrosive (C) | ExternalMSDS = [http://msds.chem.ox.ac.uk/PA/paraformaldehyde.html Oxford MSDS] | FlashPt = | Autoignition = }} }} '''Paraformaldehyde''', also known as '''polyoxymethylene''', is the [[condensation]] product of [[formaldehyde]] with a typical chain length of 8 - 100 units. Long chain-length (high molecular weight) paraformaldehyde is used as a [[thermoplastic]] and is known known as [[polyoxymethylene plastic]] (POM, ''Delrin'', polyformaldehyde). Paraformaldehyde commonly has a slight odor of formaldehyde due to decomposition. Paraformaldehyde is a poly-[[acetal]]. Paraformaldehyde is used as [[fumigant]], [[disinfectant]], and [[fungicide]], and for the preparation of pure formaldehyde. == Synthesis == Paraformaldehyde forms slowly in [[formaldehyde]] solutions (formaline) as a white precipitate, especially if stored in the cold. Formaline actually contains very little monomeric formaldehyde most of it forms short chains of polyformaldehyde. A few percent of [[methanol]] is often added as a [[stabilizer]] to limit the extent of [[polymerization]]. == Reactions == Paraformaldehyde can be [[depolymerization|depolymerized]] to formaldehyde gas by dry heating and to formaldehyde solution by [[water (molecule)|water]] in the presence of [[acid]] or heat. The very pure formaldehyde solutions obtained in this way are used as a [[fixation (histology)|fixative]] for [[microscopy]] and [[histology]]. Paraformaldehyde is flammable as it decomposes in the heat into the flammable gas formaldehyde. == Toxicity == As a formaldehyde releasing agent, paraformaldehyde is a suspected carcinogen. Its acute oral [[LD50|LD<sub>50</sub>]] in rats is 592&nbsp;mg/kg. == See also == * [[Polyoxymethylene plastic]] * [[1,3,5-Trioxane]], the cyclic trimer of formaldehyde * [[Polymer]] == References == <references/> [[Category:Polyethers]] [[Category:Acetals]] [[cs:Paraformaldehyd]] [[de:Paraformaldehyd]] [[ca:Poliacetal]] [[en:Polyoxymethylene]] [[es:Poliacetal]] [[it:Paraformaldeide]] [[pl:Polioksymetylen]] [[pt:Poliacetal]] [[ru:Полиформальдегид]] [[uk:Поліформальдегід]]