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Arsenic trioxide

Arsenic trioxide
Arsenic trioxide
Ball-and-stick model of the As4O6 molecule
     As3+     O2−
Names
Systematic IUPAC name
Diarsenic trioxide
Other names
Arsenic(III) oxide,
Arsenic sesquioxide,
Arseneous oxide,
Ratsbane,
Arseneous anhydride,
White arsenic
Identifiers
1327-53-3 YesY
3D model (Jmol) Interactive image
ChEMBL ChEMBL1200978 N
ChemSpider 452539 YesY
DrugBank DB01169 YesY
ECHA InfoCard 100.014.075
EC Number 215-481-4
KEGG C13619 N
PubChem 261004
RTECS number CG3325000
UNII S7V92P67HO YesY
Properties
As
2O
3
Molar mass 197.841 g/mol
Appearance White solid
Density 3.74 g/cm3
Melting point 312.2 °C (594.0 °F; 585.3 K)
Boiling point 465 °C (869 °F; 738 K)
20 g/L (25 °C)
see text
Solubility soluble in dilute acids and alkalies, practically insoluble in organic solvents
Acidity (pKa) 9.2
Structure
cubic (α)<180 °C
monoclinic (β) >180 °C
See text
Zero
Thermochemistry
 ? J.K−1.mol−1
−657.4 kJ/mol
Pharmacology
L01XX27 (WHO)
Pharmacokinetics:
75% bound
Hazards
Safety data sheet See: data page
Very Toxic T+ Dangerous for the Environment (Nature) N
R-phrases R45, R28, R34,
R50/53
S-phrases S53, S45, S60,
S61
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Lethal dose or concentration (LD, LC):
LD50 (median dose)
 14.6 mg/kg (rat, oral)
US health exposure limits (NIOSH):
PEL (Permissible)
 [1910.1018] TWA 0.010 mg/m3
REL (Recommended)
 Ca C 0.002 mg/m3 [15-minute]
IDLH (Immediate danger)
 Ca [5 mg/m3 (as As)]
Related compounds
Other anions
Arsenic trisulfide
Other cations
Phosphorus trioxide
Antimony trioxide
Related compounds
 Arsenic pentoxide
Arsenous acid
Supplementary data page
Refractive index (n),
Dielectric constant (εr), etc.
Thermodynamic
data
 Phase behaviour
solid–liquid–gas
UV, IR, NMR, MS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YesYN ?)
Infobox references

Arsenic trioxide is an inorganic compound with the formula As
2O
3. This commercially important oxide of arsenic is the main precursor to other arsenic compounds, including organoarsenic compounds. Approximately 50,000 tonnes are produced annually. Many applications are controversial given the high toxicity of arsenic compounds.

Arsenic trioxide can be generated via routine processing of arsenic compounds including the oxidation (combustion) of arsenic and arsenic-containing minerals in air. Illustrative is the roasting of orpiment, a typical arsenic sulfide ore.

Most arsenic oxide is, however, obtained as a volatile by-product of the processing of other ores. For example, arsenopyrite, a common impurity in gold- and copper-containing ores, liberates arsenic trioxide upon heating in air. The processing of such minerals has led to numerous cases of poisonings. Only in China are arsenic ores intentionally mined.

In the laboratory, it is prepared by hydrolysis of arsenic trichloride:

As
2O
3 occurs naturally as two minerals, arsenolite (cubic) and claudetite (monoclinic). Both are relatively rare secondary minerals found in oxidation zones of As-rich ore deposits. Sheets of As2O3 stand for part of structures of the recently discovered minerals lucabindiite, (K,NH4)As4O6(Cl,Br), and its sodium-analogue torrecillasite.


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