Phosphorus tetroxide

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General
Surname Phosphorus tetroxide
Molecular formula P 2 O 4
External identifiers / databases
CAS number 12137-38-1
Wikidata Q656574
properties
Molar mass 125.96 g mol −1
Physical state

firmly

density

2.54 g cm −3

Melting point

> 100 ° C

safety instructions
GHS hazard labeling
no classification available
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Phosphorus tetroxide ( phosphorus tetraoxide, diphosphorus tetraoxide ) is a chemical compound made up of the elements phosphorus and oxygen and is one of the oxides of phosphorus. The empirical formula is given as P 2 O 4 , although this does not quite do justice to the structure or the stoichiometry of the compound.

Extraction and presentation

Phosphorus tetroxide can be obtained by thermal decomposition of phosphorus trioxide :

Phosphorus trioxide disproportionates to phosphorus and phosphorus tetroxide above 210 ° C.

Furthermore can the phosphorus trioxide by a controlled oxidation with oxygen in a carbon tetrachloride - solution are converted into phosphorus tetroxide.

If phosphorus pentoxide is carefully reduced with red phosphorus at 450–525 ° C, phosphorus tetroxide is formed.

properties

Phosphorus tetroxide is a colorless, solid mixed oxide that crystallizes differently depending on the manufacturing process . The so-called α-form forms rhombohedral crystals and consists of P 4 O 8 and P 4 O 9 - molecules in varying amounts. Instead of the above-mentioned empirical formula are added to this form of Phosphortetroxids the ratio formula P 4 O from 8.1 to 9.0 at. Monoclinic crystallizes the β form, consisting of P 4 O 7 and P 4 O 8 . The ratio formula here is P 4 O 7.7–8.0 .

Phosphorus tetroxide reacts with water ( hydrolysis ) to form phosphonic and phosphoric acid .

Individual evidence

  1. ↑ a b Entry on phosphorus oxides. In: Römpp Online . Georg Thieme Verlag, accessed on September 30, 2014.
  2. ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
  3. ↑ a b c Ralf Steudel : Chemistry of Non-Metals, Syntheses - Structures - Bonding - Use , 4th Edition, 2014 Walter de Gruyter GmbH & Co. KG, Berlin / Boston, ISBN 978-3-11-030439-8 , p. 408-409, (accessed via De Gruyter Online).