Paraformaldehyde
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| Names | |
|---|---|
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IUPAC name
Polyoxymethylene
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| Identifiers | |
| ChemSpider |
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| ECHA InfoCard | 100.108.270 |
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PubChem CID
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| Properties | |
| OH(CH2O)nH (n = 8 - 100) | |
| Appearance | white crystalline solid |
| Density | 1.42 g·cm−3 (25 °C) |
| Melting point | 120 °C (248 °F; 393 K) |
| low | |
| Hazards | |
| Safety data sheet | Oxford MSDS |
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EU classification (DSD)
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Toxic (T); Corrosive (C) |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 (what is   ?) |
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| Infobox references | |
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.
Paraformaldehyde forms slowly in aqueous formaldehyde solutions as a white precipitate, especially if stored in the cold. Formalin actually contains very little monomeric formaldehyde; most of it forms short chains of polyformaldehyde. A small amount of methanol is often added as a stabilizer to limit the extent of polymerization.
Paraformaldehyde can be depolymerized to formaldehyde gas by dry heating and to form a formaldehyde solution by water in the presence of a base or heat. The very pure formaldehyde solutions obtained in this way are used as a fixative for microscopy and histology.
The resulting formaldehyde gas from dry heating paraformaldehyde is flammable.
Once paraformaldehyde is depolymerized, the resulting formaldehyde may be used as a fumigant, disinfectant, fungicide, and fixative. Longer chain-length (high molecular weight) polyoxymethylenes are used as a thermoplastic and are known as polyoxymethylene plastic (POM, Delrin). It was used in the past in the discredited Sargenti method of root canal treatment.
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