Arsenic pentoxide

Diarsenic pentoxide

Names
Other names

Arsenic(V) oxide
Neutral arsenic oxide (2:5)
Arsenic anhydride

Identifiers

CAS Number

* 1303-28-2 Y

3D model (JSmol)

* Interactive image

ChemSpider |

* 14088 Y

EC Number |

* 215-116-9

PubChem CID

* 14771

RTECS number |

* CG2275000

UNII |

* 4GWL8T475I

UN number | 1559

InChI

* InChI=1S/As2O5/c3-1(4)7-2(5)6 Y

Key: COHDHYZHOPQOFD-UHFFFAOYSA-N Y

* InChI=1/As2O5/c3-1(4)7-2(5)6

Key: COHDHYZHOPQOFD-UHFFFAOYAN

SMILES

* O=[As](=O)O[As](=O)=O

Properties

Chemical formula

| As2O5
Molar mass | 229.8402 g/mol
Appearance  | white hygroscopic powder
Density | 4.32 g/cm3
Melting point |  315 °C (599 °F; 588 K) (decomposes)

Solubility in water

| 59.5 g/100 mL (0 °C)
65.8 g/100 mL (20 °C)
8.20 g/100 mL (100 °C)
Solubility | soluble in alcohol
Acidity (pKa)  | 7
Hazards
GHS pictograms |
GHS Signal word | Danger

GHS hazard statements

| H301, H331, H350, H410

GHS precautionary statements

| P201, P202, P261, P264, P270, P271, P273, P281, P301+310, P304+340, P308+313, P311, P321, P330, P391, P403+233, P405, P501
NFPA 704 (fire diamond)  |

Lethal dose or concentration (LD, LC):

LD50 (median dose)

| 8 mg/kg (rat, oral)
NIOSH (US health exposure limits):

PEL (Permissible)

| [1910.1018] TWA 0.010 mg/m3[1]

REL (Recommended)

| Ca C 0.002 mg/m3 [15-minute][1]

IDLH (Immediate danger)

| Ca [5 mg/m3 (as As)][1]
Related compounds

Other cations

| Phosphorus pentoxide
Antimony pentoxide

Related compounds

| Arsenic trioxide
Arsenic acid

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Y verify (what is YN ?)
Infobox references

Arsenic pentoxide is the inorganic compound with the formula As2O5.[2] This glassy, white, deliquescent solid is relatively unstable, consistent with the rarity of the As(V) oxidation state. More common, and far more important commercially, is arsenic(III) oxide (As2O3). All inorganic arsenic compounds are highly toxic and thus find only limited commercial applications.

## Contents

* 1 Structure
* 2 Synthesis
* 2.1 Historical
* 2.2 Modern methods
* 3 Safety
* 4 References
* 5 External links

## Structure

The structure consists of tetrahedral {AsO4} and octahedral {AsO6} centers linked by sharing corners.[3] The structure differs from that of the corresponding phosphorus(V) oxide; as a result, although there is still a solid solution with that oxide, it only progresses to the equimolar point, at which point phosphorus has substituted for arsenic in all of its tetrahedral sites. Likewise, arsenic pentoxide can also dissolve up to an equimolar amount of antimony pentoxide, as antimony substitutes for arsenic only in its octahedral sites.[4]

| 140px |

|
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As coordination | unit cell | cell packing

## Synthesis

### Historical

Pierre Macquer found a crystallizable salt which he called ‘sel neutre arsenical’. This salt was the residue obtained after distilling nitric acid from a mixture of potassium nitrate and arsenic trioxide. Previously Paracelsus heated a mixture of arsenic trioxide and potassium nitrate. He applied the term ‘arsenicum fixum’ to the product. A. Libavius called the same product ‘butyrum arsenici’ (butter of arsenic), although this term was actually used for arsenic trichloride. The products that Paracelsus and Libavius found were all impure alkali arsenates.[5] Scheele prepared a number of arsenates by the action of arsenic acid on the alkalies. One of the arsenates that he prepared, was arsenic pentoxide.[6] The water in the alkalies evaporated at 180˚C, and the arsenic pentoxide was stable below 400˚C .[5]

### Modern methods

Arsenic pentoxide can be crystallized by heating As2O3 under oxygen. This reaction is reversible:[3]

As2O5 ⇌ As2O3 \+ O2

Strong oxidizing agents such as ozone, hydrogen peroxide, and nitric acid convert arsenic trioxide to the pentoxide.

Arsenic acid can be generated via routine processing of arsenic compounds including the oxidation of arsenic and arsenic-containing minerals in air. Illustrative is the roasting of orpiment, a typical arsenic sulfide ore:[7]

2 As2S3 \+ 11 O2 → 2 As2O5 \+ 6 SO2

## Safety

Like all inorganic arsenic compounds, the pentoxide is highly toxic. Its reduced derivative arsenite, which is an As(III) compound, is even more toxic since it has a high affinity for thiol groups of cysteine residues in proteins.

It is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities.[8]

## References

1. ↑ 1.0 1.1 1.2 NIOSH Pocket Guide to Chemical Hazards. "#0038". National Institute for Occupational Safety and Health (NIOSH). https://www.cdc.gov/niosh/npg/npgd0038.html.
2. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
3. ↑ 3.0 3.1 Martin Jansen (1977). "Crystal Structure of As2O5". Angewandte Chemie International Edition in English 16 (5): 314–315. doi:10.1002/anie.197703142.
4. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
5. ↑ 5.0 5.1 J. W. Mellor. "Comprehensive Treatise on Inorganic & Theoretical Chemistry". http://www.rexresearch.com/alchemy10/melloras.htm.
6. ↑ C.W. Zenger. "Arsenic 149". http://tera-3.ul.cs.cmu.edu/NASD/4dcb85c3-9fee-4c83-9e6d-fe6ce5522b59/China/disk4/75/75-2/31005153/HTML/00000166.htm.
7. ↑ Grund, S. C.; Hanusch, K.; Wolf, H. U.. "Ullmann's Encyclopedia of Industrial Chemistry". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a03_113.pub2.
8. ↑ 40 C.F.R.: Appendix A to Part 355—The List of Extremely Hazardous Substances and Their Threshold Planning Quantities (July 1, 2008 ed.). Government Printing Office. http://edocket.access.gpo.gov/cfr_2008/julqtr/pdf/40cfr355AppA.pdf. Retrieved October 29, 2011.

## External links

* NIOSH Pocket Guide to Chemical Hazards
* IARC Monograph – Arsenic and Arsenic Compounds
* NTP Report on Carcinogens – Inorganic Arsenic Compounds
* ESIS: European chemical Substances Information System
* Linstrom, Peter J.; Mallard, William G. (eds.); NIST Chemistry WebBook, NIST Standard Reference Database Number 69, National Institute of Standards and Technology, Gaithersburg (MD), http://webbook.nist.gov

* v
* t
* e

Arsenic compounds

* AsBr3
* AsCl3
* AsCl5
* AsF3
* AsF5
* AsH3
* AsHgI4
* AsI3
* As2O3
* As2O5
* As2S3
* As2S5
* As2Se3
* As4S4

* v
* t
* e

Oxides

Mixed oxidation states|

* Antimony tetroxide (Sb2O4)
* Cobalt(II,III) oxide (Co3O4)
* Europium(II,III) oxide (Eu3O4)
* Iron(II,III) oxide (Fe<sub>3O4)
* Lead(II,IV) oxide (Pb3O4)
* Manganese(II,III) oxide (Mn3O4)
* Silver(I,III) oxide (Ag2O2)
* Triuranium octoxide (U3O8)
* Carbon suboxide (C3O2)
* Mellitic anhydride (C12O9)
* [[Chemistry:Praseodymium(III,IV) Praseodymium(III,IV) oxide]] (Pr6O11)
* Terbium(III,IV) oxide (Tb4O7)

+1 oxidation state|

* Copper(I) oxide (Cu<sub>2O)
* Caesium oxide (Cs2O)
* Dicarbon monoxide (C2O)
* Dichlorine monoxide (Cl2O)
* Gallium(I) oxide (Ga2O)
* Lithium oxide (Li2O)
* Potassium oxide (K2O)
* Rubidium oxide (Rb2O)
* Silver oxide (Ag2O)
* Thallium(I) oxide (Tl2O)
* Sodium oxide (Na2O)
* Water (hydrogen oxide) (H2O)

+2 oxidation state|

* Aluminium(II) oxide (AlO)
* Barium oxide (BaO)
* Beryllium oxide (BeO)
* Cadmium oxide (CdO)
* Calcium oxide (CaO)
* Carbon monoxide (CO)
* Chromium(II) oxide (CrO)
* Cobalt(II) oxide (CoO)
* Copper(II) oxide (CuO)
* Europium(II) oxide (EuO)
* Germanium monoxide (GeO))
* Iron(II) oxide (FeO)
* Lead(II) oxide (PbO)
* Magnesium oxide (MgO)
* Manganese(II) oxide (MnO)
* Mercury(II) oxide (HgO)
* Nickel(II) oxide (NiO)
* Nitric oxide (NO)
* Palladium(II) oxide (PdO)
* Silicon monoxide (SiO)
* Strontium oxide (SrO)
* Sulfur monoxide (SO)
* Disulfur dioxide (S2O2)
* Thorium monoxide (ThO)
* Tin(II) oxide (SnO)
* Titanium(II) oxide (TiO)
* Vanadium(II) oxide (VO)
* Zinc oxide (ZnO)

+3 oxidation state|

* Aluminium oxide (Al<sub>2O3)
* Antimony trioxide (Sb2O3)
* Arsenic trioxide (As2O3)
* Bismuth(III) oxide (Bi2O3)
* Boron trioxide (B2O3)
* Cerium(III) oxide (Ce2O3)
* Dibromine trioxide (Br2O3)
* Chromium(III) oxide (Cr2O3)
* Dinitrogen trioxide (N2O3)
* Dysprosium(III) oxide (Dy2O3)
* Erbium(III) oxide (Er2O3)
* Europium(III) oxide (Eu2O3)
* Gadolinium(III) oxide (Gd2O3)
* Gallium(III) oxide (Ga2O3)
* Holmium(III) oxide (Ho2O3)
* Indium(III) oxide (In<sub>2O3)
* Iron(III) oxide (Fe2O3)
* Lanthanum oxide (La2O3)
* Lutetium(III) oxide (Lu2O3)
* Manganese(III) oxide (Mn2O3)
* Neodymium(III) oxide (Nd2O3)
* Nickel(III) oxide (Ni2O3)
* Phosphorus trioxide (P4O6)
* Praseodymium(III) oxide (Pr2O3)
* Promethium(III) oxide (Pm2O3)
* Rhodium(III) oxide (Rh2O3)
* [[Chemistry:Samarium(III) Samarium(III) oxide]] (Sm2O3)
* Scandium oxide (Sc2O3)
* Terbium(III) oxide (Tb2O3)
* Thallium(III) oxide (Tl2O3)
* Thulium(III) oxide (Tm2O3)
* Titanium(III) oxide (Ti2O3)
* Tungsten(III) oxide (W2O3)
* Vanadium(III) oxide (V2O3)
* Ytterbium(III) oxide (Yb2O3)
* Yttrium(III) oxide (Y2O3)

+4 oxidation state|

* Americium dioxide (AmO2)
* Carbon dioxide (CO2)
* Carbon trioxide (CO3)
* Cerium(IV) oxide (CeO2)
* Chlorine dioxide (ClO2)
* Chromium(IV) oxide (CrO<sub>2)
* Dinitrogen tetroxide (N2O4)
* Germanium dioxide (GeO<sub>2)
* [[Chemistry:Hafnium(IV) Hafnium(IV) oxide]] (HfO2)
* Lead dioxide (PbO2)
* Manganese dioxide (MnO2)
* Neptunium(IV) oxide (NpO2)
* Nitrogen dioxide (NO2)
* Osmium dioxide (OsO2)
* Plutonium(IV) oxide (PuO2)
* Praseodymium(IV) oxide (PrO2)
* Protactinium(IV) oxide (PaO2)
* Rhodium(IV) oxide (RhO2)
* Ruthenium(IV) oxide (RuO<sub>2)
* Selenium dioxide (SeO2)
* Silicon dioxide (SiO2)
* Sulfur dioxide (SO2)
* Tellurium dioxide (TeO<sub>2)
* [[Chemistry:Terbium(IV) Terbium(IV) oxide]] (TbO2)
* Thorium dioxide (ThO2)
* Tin dioxide (SnO2)
* Titanium dioxide (TiO<sub>2)
* Tungsten(IV) oxide (WO2)
* Uranium dioxide (UO2)
* Vanadium(IV) oxide (VO2)
* Zirconium dioxide (ZrO2)

+5 oxidation state|

* Antimony pentoxide (Sb2O5)
* Arsenic pentoxide (As2O5)
* Dinitrogen pentoxide (N2O5)
* Niobium pentoxide (Nb2O5)
* Phosphorus pentoxide (P2O5)
* Protactinium(V) oxide (Pa2O5)
* Tantalum pentoxide (Ta2O5)
* Vanadium(V) oxide (V2O5)

+6 oxidation state|

* Chromium trioxide (CrO3)
* Molybdenum trioxide (MoO3)
* Rhenium trioxide (ReO3)
* Selenium trioxide (SeO3)
* Sulfur trioxide (SO3)
* Tellurium trioxide (TeO3)
* Tungsten trioxide (WO3)
* Uranium trioxide (UO3)
* Xenon trioxide (XeO3)
* Iridium trioxide (IrO3)

+7 oxidation state|

* Dichlorine heptoxide (Cl2O7)
* Manganese heptoxide (Mn2O7)
* [[Chemistry:Rhenium(VII) Rhenium(VII) oxide]] (Re2O7)
* Technetium(VII) oxide (Tc2O7)

+8 oxidation state|

* Osmium tetroxide (OsO4)
* Ruthenium tetroxide (RuO4)
* Xenon tetroxide (XeO4)
* Iridium tetroxide (IrO4)
* Hassium tetroxide (HsO4)

Related|

* Oxocarbon
* Suboxide
* Oxyanion
* Ozonide
* Peroxide
* Superoxide

Oxides are sorted by oxidation state. Category:Oxides

* v
* t
* e

Oxygen compounds

* AgO
* Al2O3
* AmO2
* Am2O3
* As2O3
* As2O5
* Au2O3
* B2O3
* BaO
* BeO
* Bi2O3
* BiO2
* Bi2O5
* BrO2
* Br2O3
* Br2O5
* CO
* CO2
* C2O3
* CaO
* CaO2
* CdO
* CeO2
* Ce3O4
* Ce2O3
* ClO2
* Cl2O
* Cl2O3
* Cl2O4
* Cl2O6
* Cl2O7
* CoO
* Co2O3
* Co3O4
* CrO3
* Cr2O3
* Cr2O5
* Cr5O12
* CsO2
* Cs2O3
* CuO
* D2O
* Dy2O3
* Er2O3
* Eu2O3
* FeO
* Fe2O3
* Fe3O4
* Ga2O
* Ga2O3
* GeO
* GeO2
* H2O
* H218O
* H2O2
* HfO2
* HgO
* Hg2O
* Ho2O3
* I2O4
* I2O5
* I2O6
* I4O9
* In2O3
* IrO2
* KO2
* K2O2
* La2O3
* Li2O
* Li2O2
* Lu2O3
* MgO
* Mg2O3
* MnO
* MnO2
* Mn2O3
* Mn2O7
* MoO2
* MoO3
* Mo2O3
* NO
* NO2
* N2O
* N2O3
* N2O4
* N2O5
* NaO2
* Na2O
* Na2O2
* NbO
* NbO2
* Nd2O3
* OF2
* O2F2
* O3F2
* O4F2
* O2PtF6

Chemical formulas

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*[CID]: Compound ID
*[H301]: Toxic if swallowed
*[H331]: Toxic if inhaled
*[H350]: May cause cancer
*[H410]: Very toxic to aquatic life with long lasting effects
*[P201]: Obtain special instructions before use
*[P202]: Do not handle until all safety precautions have been read and understood
*[P261]: Avoid breathing dust/fume/gas/mist/vapours/spray
*[P264]: Wash … thoroughly after handling
*[P270]: Do not eat, drink or smoke when using this product
*[P271]: Use only outdoors or in a well-ventilated area
*[P273]: Avoid release to the environment
*[P281]: Use personal protective equipment as required
*[P301+310]: IF SWALLOWED: Immediately call a POISON CENTER or doctor/physician
*[P304+340]: IF INHALED: Remove victim to fresh air and keep at rest in a position comfortable for breathing
*[P308+313]: IF exposed or concerned: Get medical advice/attention
*[P311]: Call a POISON CENTER or doctor/physician
*[P321]: Specific treatment (see … on this label)
*[P330]: Rinse mouth
*[P391]: Collect spillage
*[P403+233]: Store in a well ventilated place. Keep container tightly closed
*[P405]: Store locked up
*[P501]: Dispose of contents/container to …
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