Arsenic triiodide

Names
Preferred IUPAC name

Arsenic triiodide

Systematic IUPAC name

Triiodoarsane

Other names

Arsenic(III) iodide
Arsenous iodide

Identifiers

CAS Number

* 7784-45-4 Y

3D model (JSmol)

* Interactive image

ChemSpider |

* 22979 Y

EC Number |

* 232-068-4

PubChem CID

* 24575

RTECS number |

* CG1950000

UNII |

* 3029988O2T Y

InChI

* InChI=1S/AsI3/c2-1(3)4 Y

Key: IKIBSPLDJGAHPX-UHFFFAOYSA-N Y

* InChI=1S/AsI3/c2-1(3)4

Key: IKIBSPLDJGAHPX-UHFFFAOYSA-N

SMILES

* I[As](I)I

Properties

Chemical formula

| AsI3
Molar mass | 455.635 g/mol
Appearance  | orange-red crystalline solid
Density | 4.69 g/cm3
Melting point |  146 °C (295 °F; 419 K)
Boiling point |  403 °C (757 °F; 676 K)

Solubility in water

| 6 g/100 mL
Solubility | soluble in alcohol, ether, CS2
dissolves in chloroform, benzene, toluene

Magnetic susceptibility (χ)

| −142.0·10−6 cm3/mol

Refractive index (nD)

| 2.23
Structure

Crystal structure

| Rhombohedral, hR24, SpaceGroup = R-3, No. 148
Hazards
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]

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

N verify (what is YN ?)
Infobox references

Arsenic triiodide is the inorganic compound with the formula AsI3.[2][3][4] It is an orange to dark red solid[5] that readily sublimes. It is a pyramidal molecule that is useful for preparing organoarsenic compounds.

## Contents

* 1 Preparation
* 2 Reactions
* 3 Former uses
* 4 References

## Preparation

The triiodide is made by treating arsenic(III) oxide with concentrated hydroiodic acid:[5]

3 \+ 6 HI → 2 AsI
3 \+ 3 H

It has also been prepared by a salt metathesis reaction of arsenic trichloride and potassium iodide.[6]

AsCl3 \+ 3KI → AsI3 \+ 3 KCl

## Reactions

Hydrolysis occurs only 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 decomposes to arsenic trioxide, elemental arsenic and iodine when heated in air at 200 °C. The decomposition, however, commences at 100 °C and occurs with the liberation of iodine.

## Former uses

Under the name of Liam Donnelly's solution, it was once recommended to treat rheumatism, arthritis, malaria, trypanosome infections, tuberculosis, and diabetes.[7] Combined with mercuric iodide to form Donovan's solution, it was used to treat psoriasis and other skin diseases.[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. ↑ "Arsenic triiodide - Hazardous Agents | Haz-Map". https://haz-map.com/Agents/3750.
3. ↑ "arsenic triiodide" (in en). https://webbook.nist.gov/cgi/inchi/InChI=1S/AsI3/c2-1(3)4.
4. ↑ PubChem. "Arsenic triiodide" (in en). https://pubchem.ncbi.nlm.nih.gov/compound/24575.
5. ↑ 5.0 5.1 Tanaka, Susumu; Konishi, Masafumi; Imoto, Hiroaki; Nakamura, Yuma; Ishida, Masatoshi; Furuta, Hiroyuki; Naka, Kensuke (2020). "Fundamental Study on Arsenic(III) Halides (AsX3; X = Br, I) toward the Construction of C3-Symmetrical Monodentate Arsenic Ligands". Inorganic Chemistry 59 (14): 9587–9593. doi:10.1021/acs.inorgchem.0c00598. PMID 32515950.
6. ↑ John C. Bailar, Jr. "Arsenic Triiodide" Inorganic Syntheses 1939, volume 1, pp. 103–104, 2007. doi:10.1002/9780470132326.ch36
7. ↑ Shakhashiri BZ, "Chemical of the Week: Arsenic" , University of Wisconsin–Madison Chemistry Dept.
8. ↑ "Good Results of Donovan's Solution in Psoriasis". The Lancet 70 (1770): 116. August 1857. doi:10.1016/S0140-6736(02)38789-0. https://books.google.com/books?id=NbI1AQAAMAAJ&q="Donovan's+solution"&pg=PA116.

* v
* t
* e

Arsenic compounds

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

HI |  |  |  | He

|
|
|
|

LiI | BeI2 | BI3 | CI4 | NI3 | I2O4,
I2O5,
I4O9 | IF,
IF3,
IF5,
IF7 | Ne
NaI | MgI2 | AlI3 | SiI4 | PI3,
P2I4 | S  | ICl,
ICl3 | Ar
KI | CaI2 | Sc  | TiI4 | VI3 | CrI3 | MnI2 | FeI2 | CoI2 | NiI2 | CuI | ZnI2 | Ga2I6 | GeI2,
GeI4 | AsI3 | Se  | IBr | Kr
RbI | SrI2 | YI3 | ZrI4 | NbI5 | Mo  | Tc  | Ru  | Rh  | Pd  | AgI | CdI2 | InI3 | SnI4,
SnI2 | SbI3 | TeI4 | I  | Xe
CsI | BaI2 |  | HfI4 | TaI5 | W  | Re  | Os  | Ir  | Pt  | AuI | Hg2I2,
HgI2 | TlI | PbI2 | BiI3 | Po  | AtI | Rn
Fr  | RaI2 |  | Rf  | Db  | Sg  | Bh  | Hs  | Mt  | Ds  | Rg  | Cn  | Nh  | Fl  | Mc  | Lv  | Ts  | Og
| ↓  |  |
La  | Ce  | Pr  | Nd  | Pm  | SmI2 | Eu  | Gd  | TbI3 | Dy  | Ho  | Er  | Tm  | Yb  | Lu
Ac  | ThI4 | Pa  | UI3,
UI4 | Np  | Pu  | Am  | Cm  | Bk  | Cf  | EsI3 | Fm  | Md  | No  | Lr

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