Arsenic triiodide
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3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.029.153 |
PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |
| AsI3 | |
| Molar mass | 455.635 g/mol |
| Appearance | orange-red crystalline solid |
| Density | 4.69 g/cm3 |
| Melting point | 146 °C |
| Boiling point | 403 °C |
| 6 g/100 mL | |
| Solubility | soluble in alcohol, ether, CS2 |
Refractive index (nD)
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2.23 |
| Structure | |
| Rhombohedral, hR24, SpaceGroup = R-3, No. 148 | |
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 triiodide is the chemical compound with the formula AsI3. It is a pyramidial molecule with covalent bonding. [2] It contains arsenic in its +3 oxidation state.
Preparation
It is prepared by a reaction between arsenic(III) chloride and an iodine salt:
- AsCl3(aq) + 3KI(aq) → AsI3(aq) + 3KCl(aq)
Reactions
Hydrolysis occurs slowly in water forming arsenic trioxide and hydroiodic acid. The reaction proceeds via formation of arsenous acid which exists in equilibrium with hydroiodic acid.
The aqueous solution is highly acidic, pH of 0.1N solution is 1.1. It readily decomposes to arsenic trioxide, elemental arsenic and iodine when heated in air at 200 °C. The decomposition, however, commences at 100 °C. A example of a decomposition reaction would be:
- 6 AsI3 + 3 O2 → 2 As2O3 + 2 As + 9 I2
Former uses
Under the name of Donovan's solution, it was once recommended to treat rheumatism, arthritis, malaria, trypanosome infections, tuberculosis, and diabetes.[1]
References
- ^ a b Shakhashiri BZ, "Chemical of the Week: Arsenic", University of Wisconsin–Madison Chemistry Dept.
- ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0070494398
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