Arsenic trisulfide

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Arsenic trisulfide
Preferred IUPAC name
Arsenic trisulfide
Other names
Arsenic(III) sulfide


Sulphuret of arsenic
  • 1303-33-9 checkY
3D model (JSmol)
ECHA InfoCard 100.013.744
EC Number
  • 215-117-4
RTECS number
  • CG2638000
  • S1[As]3S[As]2S[As](S[As]1S2)S3
Molar mass 246.02 g·mol−1
Appearance Orange crystals
Density 3.43 g cm−3
Melting point 310 °C (590 °F; 583 K)
Boiling point 707 °C (1,305 °F; 980 K)
-70.0·10−6 cm3/mol
P21/n (No. 11)
a = 1147.5(5) pm, b = 957.7(4) pm, c = 425.6(2) pm
α = 90°, β = 90.68(8)°, γ = 90°
pyramidal (As)
NFPA 704

NFPA 704.svg

U.S. Permissible
exposure limit (PEL)
[1910.1018] TWA 0.010 mg/m3
Related compounds
Other anions Arsenic trioxide
Arsenic triselenide
Other cations Phosphorus trisulfide
Antimony trisulfide
Bismuth sulfide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Arsenic trisulfide, also known as orpiment or arsenic(III) sulfide, is a chemical compound. Its chemical formula is As2S3. It has arsenic and sulfide ions in it. The arsenic is in its +3 oxidation state.

Properties[change | change source]

Arsenic trisulfide is a yellow solid. It is a semiconductor. It has a glass (amorphous) form and a crystalline form. It burns in air to make sulfur dioxide and arsenic trioxide, which makes a highly toxic smoke. Arsenic trisulfide can oxidize on the surface to make a highly toxic layer of arsenic trioxide as well. Arsenic trisulfide is not toxic unless it oxidizes. It does not react with acids.

Occurrence[change | change source]

Arsenic trisulfide is found as the mineral orpiment.

Preparation[change | change source]

Arsenic trisulfide is made when an arsenic compound like arsenic trichloride reacts with hydrogen sulfide. It is also made when arsenic and sulfur are heated together.

Uses[change | change source]

It was looked at for treating cancer. It was used by the Egyptians as a pigment and cosmetic. It is used in glass.

References[change | change source]

  1. Mullen, D. J. E.; Nowacki, W (1972), "Refinement of the crystal structures of realgar, AsS and orpiment, As2S3" (PDF), Z. Kristallogr., 136 (1–2): 48–65, doi:10.1524/zkri.1972.136.1-2.48.

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