Arsenic pentasulfide

Arsenic pentasulfide is an inorganic compound containing arsenic and sulfur.^[1]

Arsenic pentasulfide

Names
IUPAC name Arsenic pentasulfide
Other names Arsenic(V) sulfide Diarsenic pentasulfide
Identifiers
CAS Number	1303-34-0 N
3D model (JSmol)	Interactive image Interactive image
ChemSpider	2617071 Y
ECHA InfoCard	100.154.195
EC Number	625-728-1
PubChem CID	3371533
UNII	QT80493YBG
UN number	1557
CompTox Dashboard (EPA)	DTXSID0058302
InChI InChI=1S/As2S5/c3-1(4)7-2(5)6 Y Key: AYRZLUSHOXJGKY-UHFFFAOYSA-N Y InChI=1S/As4S10/c5-1-9-2(6)12-3(7,10-1)14-4(8,11-1)13-2 Key: CHQYGMAMCBQSIU-UHFFFAOYSA-N
SMILES S=[As](=S)S[As](=S)=S S=[As]12S[As]3(=S)S[As](=S)(S1)S[As](=S)(S2)S3
Properties
Chemical formula	As2S5
Molar mass	310.14 g·mol−1
Appearance	Vivid, dark orange, opaque crystals
Melting point	300 °C (572 °F; 573 K)(minimum)
Boiling point	500 °C (932 °F; 773 K)(decomposes)
Solubility in water	0.014 g dm−3 (at 0 °C)
Hazards
GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H301, H331, H410
Precautionary statements	P261, P264, P270, P271, P273, P301+P310, P304+P340, P311, P321, P330, P391, P403+P233, P405, P501
Related compounds
Related compounds	Arsenic pentoxide Arsenic trisulfide Phosphorus pentasulfide
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

Uses

Solids of the approximate formula As₂S₅ have been used as pigments and chemical intermediates but are generally only of interest in academic laboratories.^[2]

Preparation

Arsenic pentasulfide is prepared by precipitation from an acidic solution of soluble As(V) salts by treatment with hydrogen sulfide.^[3] It may be also prepared by heating a mixture of arsenic and sulfur, extracting the fused mass with an ammonia solution and reprecipitating arsenic pentasulfide at low temperature by addition of hydrochloric acid.

Phosphorus pentasulfide with the formula P₄S₁₀, is a molecular compound featuring tetrahedral phosphorus(V) centres. Trends in arsenic redox potentials suggest that As₂S₅ adopts a similar structure, a plausible alternative being an arsenic polysulfide.

Reactions

Arsenic pentasulfide hydrolyzes in boiling water, giving arsenous acid and sulfur:

As₂S₅ + 6 H₂O → 2 H₃AsO₃ + 2 S + 3 H₂S

It oxidizes in air at elevated temperatures producing arsenic oxides, the products and yields of which are variable. In alkali metal sulfide solutions arsenic pentasulfide forms a thioarsenate anion, [AsS₄]³⁻, which contain As(V) centres.