| IUPAC name
| Other names
Butter of arsenic
de Valagin's solution
|Molar mass||181.28 g/mol|
|Density||2.163 g/cm3 (20 °C)|
|Melting point||−16.2 °C (2.8 °F; 256.9 K)|
|Boiling point||130.2 °C (266.4 °F; 403.3 K)|
|Solubility|| Reacts with alcohols|
Miscible with carbon tetrachloride, chloroform, diethyl ether, hydrochloric acid, phosphorus trichloride, THF, toluene, xylene
|Vapor pressure||8.78 mmHg at 20 °C|
|Safety data sheet||Sigma-Aldrich|
|Lethal dose or concentration (LD, LC):|
LD50 (Median dose)
| 48 mg/kg (rat, oral)|
80 mg/kg (rat, dermal)
| Nitrogen trichloride|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Arsenic(III) chloride or arsenic trichloride is an inorganic compound with the formula AsCl3. It is highly corrosive and poisonous.
As arsenic is in group 15, it can also form arsenic pentachloride (AsCl5). However, this compound is unstable at temperatures above −50 °C, meaning it has no uses in chemistry except for research.
- AsCl3 + 3 H2O → As(OH)3 + 3 HCl
Although AsCl3 is less moisture sensitive than PCl3, it still fumes in moist air.
AsCl3 undergoes redistribution upon treatment with As2O3 to give arsenic oxychloride, AsOCl.
- AsCl3 + As2O3 → 3 AsOCl
- AsCl3 + 3 KBr → AsBr3 + 3 KCl
- AsCl3 + 3 KI → AsI3 + 3 KCl
Arsenic trichloride is a colorless liquid, that fumes in moist air. Impure samples may appear yellowish or cloudy. It reacts with water and alcohols, but it's miscible with ethers.
Arsenic(III) chloride is sold by chemical suppliers, however due to its hazards, and the fact that arsenic compounds are highly regulated in most countries, it's practically impossible for the hobby chemist to acquire it.
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.
There are several preparation routes:
- As2O3 + 6 HCl → 2 AsCl3 + 3 H2O
- 2 As2O3 + 6 S2Cl2 → 4 AsCl3 + 3 SO2 + 9 S
- 2 As2O3 + 3 SOCl2 → 2 AsCl3 + 3 SO2
In all these cases, the reaction takes place during reflux. The final product is distilled.
A water-free route, which gives a very pure product, involves direct chlorination of arsenic at 80–85 °C, but this method requires elemental arsenic, which is volatile and more hazardous:
- 2 As + 3 Cl2 → 2 AsCl3
- Make organoarsenic compounds (don't you have better things to do, though?)
- Make arsenic bromides and iodides
- Compound collecting
Arsenic and all of its compounds are highly toxic, and AsCl3 more so, because of its volatility and solubility.
Arsenic trichloride must be kept away from moisture. Schlenck flasks or ampouling are recommended.
The neutralization of arsenic halides is complicated not only by their volatility, but also by the high toxicity of arsenic compounds. Any neutralization must be done in a special installation, designed to scrub any traces of arsenic wastes.
- R. C. Smith, "Manufacture of Arsenic trichloride" The Journal of Industrial and Engineering Chemistry 1919, volume 11, pp. 109–110
- S. K. Pandey, A. Steiner, H. W. Roesky, S. Kamepalli, A. H. Cowley, "Arsenic(III)chloride" Inorganic Synthesis 1997, volume 31, pp. 148-150
- A TEXT-BOOK OF INORGANIC CHEMISTRY. VOLUME XI. ORGANOMETALLIC COMPOUNDS. PART II. DERIVATIVES OF ARSENIC.