Arsenic pentoxide
Names | |
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Other names
Arsenic(V) oxide
Neutral arsenic oxide (2:5) Arsenic anhydride | |
Identifiers | |
3D model (
JSmol ) |
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ChemSpider | |
ECHA InfoCard
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100.013.743 |
EC Number |
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PubChem CID
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RTECS number
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UNII | |
UN number | 1559 |
CompTox Dashboard (EPA)
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Properties | |
As2O5 | |
Molar mass | 229.8402 g/mol |
Appearance | white hygroscopic powder
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Density | 4.32 g/cm3 |
Melting point | 315 °C (599 °F; 588 K) (decomposes) |
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 labelling: | |
Danger | |
H301, H331, H350, H410 | |
P201, P202, P261, P264, P270, P271, P273, P281, P301+P310, P304+P340, P308+P313, P311, P321, P330, P391, P403+P233, P405, P501 | |
NFPA 704 (fire diamond) | |
Lethal dose or concentration (LD, LC): | |
LD50 (median dose)
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8 mg/kg (rat, oral) |
NIOSH (US health exposure limits): | |
PEL (Permissible)
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[1910.1018] TWA 0.010 mg/m3[1] |
REL (Recommended)
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Ca C 0.002 mg/m3 [15-minute][1] |
IDLH (Immediate danger) |
Ca [5 mg/m3 (as As)][1] |
Related compounds | |
Other cations
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Phosphorus pentoxide Antimony pentoxide |
Related compounds
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Arsenic trioxide Arsenic acid |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Arsenic pentoxide is the
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]
As coordination | unit cell | cell packing |
Synthesis
Historical
Modern methods
Arsenic pentoxide can be crystallized by heating As2O3 under oxygen. This reaction is reversible:[3]
- As2O5 ⇌ As2O3 + O2
Strong
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
References
- ^ a b c NIOSH Pocket Guide to Chemical Hazards. "#0038". National Institute for Occupational Safety and Health (NIOSH).
- ISBN 978-0-08-037941-8.
- ^ .
- ISBN 978-0-08-037941-8.
- ^ a b J. W. Mellor. "Comprehensive Treatise on Inorganic & Theoretical Chemistry". Archived from the original on 2012-05-11. Retrieved 2013-03-30.
- ^ C.W. Zenger; et al. "Arsenic 149". Archived from the original on 2013-04-09.
- ISBN 978-3527306732.
- ^ "40 C.F.R.: Appendix A to Part 355—The List of Extremely Hazardous Substances and Their Threshold Planning Quantities" (PDF) (July 1, 2008 ed.). Government Printing Office. Archived from the original (PDF) on February 25, 2012. Retrieved October 29, 2011.
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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)