Arsenic pentoxide

Last updated
Diarsenic pentoxide
Arsenic-pentoxide-3D-polyhedra.png
Names
Other names
Arsenic(V) oxide
Neutral arsenic oxide (2:5)
Arsenic anhydride
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.013.743 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 215-116-9
PubChem CID
RTECS number
  • CG2275000
UNII
UN number 1559
  • InChI=1S/As2O5/c3-1(4)7-2(5)6 Yes check.svgY
    Key: COHDHYZHOPQOFD-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/As2O5/c3-1(4)7-2(5)6
    Key: COHDHYZHOPQOFD-UHFFFAOYAN
  • O=[As](=O)O[As](=O)=O
Properties
As2O5
Molar mass 229.8402 g/mol
Appearancewhite hygroscopic powder
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:
GHS-pictogram-skull.svg GHS-pictogram-silhouette.svg GHS-pictogram-pollu.svg
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)
4
0
0
Lethal dose or concentration (LD, LC):
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).
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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

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]

Arsenic-pentoxide-As-coordination-3D-balls.png Arsenic-pentoxide-unit-cell-3D-balls.png Arsenic-pentoxide-3D-balls-A.png
As coordinationunit cellcell 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]

Related Research Articles

<span class="mw-page-title-main">Arsenic</span> Chemical element, symbol As and atomic number 33

Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, but only the gray form, which has a metallic appearance, is important to industry.

<span class="mw-page-title-main">Antimony</span> Chemical element, symbol Sb and atomic number 51

Antimony is a chemical element with the symbol Sb (from Latin stibium) and atomic number 51. A lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb2S3). Antimony compounds have been known since ancient times and were powdered for use as medicine and cosmetics, often known by the Arabic name kohl. The earliest known description of the metal in the West was written in 1540 by Vannoccio Biringuccio.

An acidic oxide is an oxide that either produces an acidic solution upon addition to water, or acts as an acceptor of hydroxide ions effectively functioning as a Lewis acid. Acidic oxides will typically have a low pKa and may be inorganic or organic. A commonly encountered acidic oxide, carbon dioxide produces an acidic solution when dissolved.

<span class="mw-page-title-main">Arsenic trioxide</span> Chemical compound (industrial chemical and medication)

Arsenic trioxide, sold under the brand name Trisenox among others, is an inorganic compound with the formula As
2O
3. As an industrial chemical, its major uses include the manufacture of wood preservatives, pesticides, and glass. It is also used as a medication to treat a type of cancer known as acute promyelocytic leukemia. For this use it is given by injection into a vein.

<span class="mw-page-title-main">Antimony trioxide</span> Chemical compound

Antimony(III) oxide is the inorganic compound with the formula Sb2O3. It is the most important commercial compound of antimony. It is found in nature as the minerals valentinite and senarmontite. Like most polymeric oxides, Sb2O3 dissolves in aqueous solutions with hydrolysis. A mixed arsenic-antimony oxide occurs in nature as the very rare mineral stibioclaudetite.

<span class="mw-page-title-main">Arsenic acid</span> Chemical compound

Arsenic acid or trihydrogen arsenate is the chemical compound with the formula H3AsO4. More descriptively written as AsO(OH)3, this colorless acid is the arsenic analogue of phosphoric acid. Arsenate and phosphate salts behave very similarly. Arsenic acid as such has not been isolated, but is only found in solution, where it is largely ionized. Its hemihydrate form (2H3AsO4·H2O) does form stable crystals. Crystalline samples dehydrate with condensation at 100 °C.

In chemistry an antimonate is a compound which contains a metallic element, oxygen, and antimony in an oxidation state of +5. These compounds adopt polymeric structures with M-O-Sb linkages. They can be considered to be derivatives of the hypothetical antimonic acid H3SbO4, or combinations of metal oxides and antimony pentoxide, Sb2O5.

<span class="mw-page-title-main">Arsenous acid</span> Chemical compound

Arsenous acid (or arsenious acid) is the inorganic compound with the formula H3AsO3. It is known to occur in aqueous solutions, but it has not been isolated as a pure material, although this fact does not detract from the significance of As(OH)3.

<span class="mw-page-title-main">Antimony pentachloride</span> Chemical compound

Antimony pentachloride is a chemical compound with the formula SbCl5. It is a colourless oil, but typical samples are yellowish due to dissolved chlorine. Owing to its tendency to hydrolyse to hydrochloric acid, SbCl5 is a highly corrosive substance and must be stored in glass or PTFE containers.

<span class="mw-page-title-main">Antimony pentoxide</span> Chemical compound

Antimony pentoxide (molecular formula: Sb2O5) is a chemical compound of antimony and oxygen. It contains antimony in the +5 oxidation state.

<span class="mw-page-title-main">Antimony trichloride</span> Chemical compound

Antimony trichloride is the chemical compound with the formula SbCl3. It is a soft colorless solid with a pungent odor and was known to alchemists as butter of antimony.

Selenium trioxide is the inorganic compound with the formula SeO3. It is white, hygroscopic solid. It is also an oxidizing agent and a Lewis acid. It is of academic interest as a precursor to Se(VI) compounds.

Antimony trifluoride is the inorganic compound with the formula SbF3. Sometimes called Swarts' reagent, is one of two principal fluorides of antimony, the other being SbF5. It appears as a white solid. As well as some industrial applications, it is used as a reagent in inorganic and organofluorine chemistry.

<span class="mw-page-title-main">Antimony tetroxide</span> Chemical compound

Antimony tetroxide is an inorganic compound with the formula Sb2O4. This material, which exists as the mineral cervantite, is white but reversibly yellows upon heating. The material, with empirical formula SbO2, is called antimony tetroxide to signify the presence of two kinds of Sb centers.

Arsenic pentafluoride is a chemical compound of arsenic and fluorine. It is a toxic, colorless gas. The oxidation state of arsenic is +5.

<span class="mw-page-title-main">Bismuth trifluoride</span> Chemical compound

Bismuth(III) fluoride or bismuth trifluoride is a chemical compound of bismuth and fluorine. The chemical formula is BiF3. It is a grey-white powder melting at 649 °C.

<span class="mw-page-title-main">Dinitrogen trioxide</span> Chemical compound

Dinitrogen trioxide (also known as nitrous anhydride) is the chemical compound with the formula N2O3. It is one of the simple nitrogen oxides. It forms upon mixing equal parts of nitric oxide and nitrogen dioxide and cooling the mixture below −21 °C (−6 °F):

<span class="mw-page-title-main">Arsenic pentasulfide</span> Chemical compound

Arsenic pentasulfide is an inorganic compound containing arsenic and sulfur.

<span class="mw-page-title-main">Antimony(III) sulfate</span> Chemical compound

Antimony sulfate, Sb2(SO4)3, is a hygroscopic salt formed by reacting antimony or its compounds with hot sulfuric acid. It is used in doping of semiconductors and in the production of explosives and fireworks.

<span class="mw-page-title-main">Arsenic compounds</span> Chemical compounds containing arsenic

Compounds of arsenic resemble in some respects those of phosphorus which occupies the same group (column) of the periodic table. The most common oxidation states for arsenic are: −3 in the arsenides, which are alloy-like intermetallic compounds, +3 in the arsenites, and +5 in the arsenates and most organoarsenic compounds. Arsenic also bonds readily to itself as seen in the square As3−
4 ions in the mineral skutterudite. In the +3 oxidation state, arsenic is typically pyramidal owing to the influence of the lone pair of electrons.

References

  1. 1 2 3 NIOSH Pocket Guide to Chemical Hazards. "#0038". National Institute for Occupational Safety and Health (NIOSH).
  2. ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN   978-0-08-037941-8.
  3. 1 2 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. 1 2 J. W. Mellor. "Comprehensive Treatise on Inorganic & Theoretical Chemistry". Archived from the original on 2012-05-11. Retrieved 2013-03-30.
  6. ↑ C.W. Zenger; et al. "Arsenic 149". Archived from the original on 2013-04-09.
  7. ↑ Grund, S. C.; Hanusch, K.; Wolf, H. U. "Arsenic and Arsenic Compounds". 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" (PDF) (July 1, 2008 ed.). Government Printing Office. Archived from the original (PDF) on February 25, 2012. Retrieved October 29, 2011.{{cite journal}}: Cite journal requires |journal= (help)
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