A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can
Arsenic trisulfide is the
chemical compoundA chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
with the formula
As2Arsenic is the chemical element that has the symbol As, atomic number 33 and atomic mass 74.92. Arsenic was first documented by Albertus Magnus in 1250. Arsenic is a notoriously poisonous metalloid with many allotropic forms, including a yellow and several black and grey forms...
S3Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant, multivalent non-metal. Sulfur, in its native form, is a yellow crystalline solid. In nature, it can be found as the pure element and as sulfide and sulfate minerals...
. This bright yellow solid is well known because it occurs as the mineral
orpimentOrpiment, As2S3, is a common monoclinic arsenic sulfide mineral. It has a Mohs hardness of 1.5 to 2 and a specific gravity of 3.46. It melts at 300 °C to 325 °C...
(Latin: auripigment), has been used as a pigment, and has played a role in the analysis of arsenic compounds. This
chalcogenideA chalcogenide is a chemical compound consisting of at least one chalcogen ion and at least one more electropositive element. Although all group 16 elements of the periodic table are defined as chalcogens, the term is more commonly reserved for sulfides, selenides, and tellurides, rather than...
material is a group V/VI, intrinsic p-type, semiconductor and exhibits photo-induced phase-change properties.
The other important As-S phase is
realgarRealgar, α-As
4S
4, is an arsenic sulfide mineral. It is a soft, sectile mineral occurring in monoclinic crystals, or in granular, compact, or powdery form, often in association with the related mineral, orpiment . It is orange-red in colour, melts at 320 °C, and burns with a...
, As
4S
4, which is red-orange and also occurs as a mineral.
Structure
As
2S
3 occurs both in crystalline and amorphous forms. Both forms feature polymeric structures consisting As(III) centers are three-fold co-ordinated by sulfide centres in a
trigonal pyramidIn chemistry, a trigonal pyramid is a molecular geometry with one atom at the apex and three atoms at the corners of a trigonal base. When all three atoms at the corners are identical, the molecule belongs to point group C3v. One example of a molecule with a trigonal pyramidal geometry...
al geometery. The sulfide centres are two-fold coordinated to two arsenic atoms. In the crystalline form, the As-S bonds form bonded sheets. The bonding between the sheets consists of van der Waals forces. The crystalline form is usually found in geological samples. Amorphous As
2S
3 does not possess a layered structure but is more highly cross-linked. Like other glasses, there is no medium or long-range order, but the first co-ordination sphere is well defined. As
2S
3 is a good glass former and exhibits a wide glass-forming region in its phase diagram.
From the elements
Amorphous As
2S
3 is obtained via the fusion of the elements at 390 °C. Rapid cooling of the reaction melt ensures the disordered arrangement of the bonds, resulting in the glass. Like other chemical syntheses, pure precursors and the exclusion of air provides purer product. The reaction can be represented with the chemical equation:
- 2 As + 3 S → As2S3
Upon heating in a vacuum, polymeric As
2S
3 "cracks" to give a mixture of molecular species, including molecular As
4S
6. As
4S
6 adopts the
adamantaneAdamantane is a colourless, crystalline compound with a camphor-like odour. With a formula C10H16, it is a cycloalkane and also the simplest diamondoid. Adamantane was discovered in petroleum in 1933. Its name derived from the Greek adamantinos , due to its diamond-like...
geometry, like that observed for P
4O
6 and As
4O
6. When a film of this material is exposed to an external energy source such as thermal energy (via thermal annealing ), electromagnetic radiation (i.e. UV lamps, lasers, electron beams)), As
4S
6 polymerizes:
- 2/n (As2S3)n As4S6
Aqueous precipitation
- See also: Qualitative inorganic analysis
Classical qualitative inorganic analysis is a method of analytical chemistry which seeks to find elemental composition of inorganic compounds. It is mainly focused on detecting ions in an aqueous solution, so that materials in other forms may need to be brought into this state before using standard...
As
2S
3 forms when aqueous solutions containing As(III) are treated with H
2S. Arsenic was in the past analyzed and assayed by this reaction, which results in the
precipitationPrecipitation is the formation of a solid in a solution during a chemical reaction. When the reaction occurs, the solid formed is called the precipitate, and the liquid remaining above the solid is called the supernate...
of As
2S
3, which is then weighed. As
2S
3 can even be precipitated in 6M HCl. As
2S
3 is so insoluble that it is not toxic. As
2S
3 characteristically dissolves upon treatment with aqueous solutions containing
sulfideA sulfide is a chemical compound containing sulfur in its lowest oxidation number of −2.- Properties :...
ions. The dissolved arsenic species is the pyramidal trianion AsS:
- As2S3 + 6 NaSH → 2 AsS + 3 H2S
As
2S
3 is the anhydride of the hypothetical thioarsenous acid, As(SH)
3. Upon treatment with
polysulfidePolysulfides are a class of chemical compounds containing chains of sulfur atoms. The two main classes of polysulfides are anions with the general formula Sn2−. These anions are the conjugate bases of the hydrogen polysulfides H2Sn...
ions, As
2S
3 dissolves to give a variety of species containing both S-S and As-S bonds. One of the more noteworthy derivatives is S
7As-S
-, a ring that contains an exocyclic sulfido center attached to the As atom. As
2S
3 also dissolves in strongly alkaline solutions to give a mixture of AsS and
AsO
{{chembox
| Name = Arsenic trisulfide
| ImageFile = Orpiment-unit-cell-3D.png
| ImageName = The unit cell of orpiment
| ImageFile1 = Orpiment_mineral.jpg
| ImageName1 = Orpiment, the mineral form of arsenic trisulfide
| OtherNames = Arsenic(III) sulfide
OrpimentOrpiment, As2S3, is a common monoclinic arsenic sulfide mineral. It has a Mohs hardness of 1.5 to 2 and a specific gravity of 3.46. It melts at 300 °C to 325 °C...
| Section1 = {{Chembox Identifiers
| CASNo = 1303-33-9
}}
| Section2 = {{Chembox Properties
| Formula = As
2S
3
| MolarMass = 246.041 g/mol
| Appearance = yellow-orange powder or crystals
| Density = 3.43 g/cm
3, solid
| Solubility = insoluble
| MeltingPt = 310 °C
| BoilingPt = 707 °C
}}
| Section7 = {{Chembox Hazards
| EUClass = not listed
| NFPA-H = 4
| NFPA-F =
| NFPA-R = 2
}}
| Section8 = {{Chembox Related
| OtherAnions = As
2O
3
| OtherCations = P
4S
6
| OtherCpds =
P4S10Phosphorus pentasulfide is the chemical compound with the formula P
4S
10. This yellow solid is an industrially important inorganic compound of phosphorus and sulfur. Commercial samples often appear greenish-gray. The compound has a low solubility in carbon disulfide and...
,
AsCl3Arsenic trichloride is the chemical compound with the formula AsCl3. The substance was known to alchemy under the name butter of arsenic.-Preparation:...
}}
}}
Arsenic trisulfide is the
chemical compoundA chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
with the formula
As2Arsenic is the chemical element that has the symbol As, atomic number 33 and atomic mass 74.92. Arsenic was first documented by Albertus Magnus in 1250. Arsenic is a notoriously poisonous metalloid with many allotropic forms, including a yellow and several black and grey forms...
S3Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant, multivalent non-metal. Sulfur, in its native form, is a yellow crystalline solid. In nature, it can be found as the pure element and as sulfide and sulfate minerals...
. This bright yellow solid is well known because it occurs as the mineral
orpimentOrpiment, As2S3, is a common monoclinic arsenic sulfide mineral. It has a Mohs hardness of 1.5 to 2 and a specific gravity of 3.46. It melts at 300 °C to 325 °C...
(Latin: auripigment), has been used as a pigment, and has played a role in the analysis of arsenic compounds. This
chalcogenideA chalcogenide is a chemical compound consisting of at least one chalcogen ion and at least one more electropositive element. Although all group 16 elements of the periodic table are defined as chalcogens, the term is more commonly reserved for sulfides, selenides, and tellurides, rather than...
material is a group V/VI, intrinsic p-type, semiconductor and exhibits photo-induced phase-change properties.
The other important As-S phase is
realgarRealgar, α-As
4S
4, is an arsenic sulfide mineral. It is a soft, sectile mineral occurring in monoclinic crystals, or in granular, compact, or powdery form, often in association with the related mineral, orpiment . It is orange-red in colour, melts at 320 °C, and burns with a...
, As
4S
4, which is red-orange and also occurs as a mineral.
Structure
As
2S
3 occurs both in crystalline and amorphous forms. Both forms feature polymeric structures consisting As(III) centers are three-fold co-ordinated by sulfide centres in a
trigonal pyramidIn chemistry, a trigonal pyramid is a molecular geometry with one atom at the apex and three atoms at the corners of a trigonal base. When all three atoms at the corners are identical, the molecule belongs to point group C3v. One example of a molecule with a trigonal pyramidal geometry...
al geometery. The sulfide centres are two-fold coordinated to two arsenic atoms. In the crystalline form, the As-S bonds form bonded sheets. The bonding between the sheets consists of van der Waals forces. The crystalline form is usually found in geological samples. Amorphous As
2S
3 does not possess a layered structure but is more highly cross-linked. Like other glasses, there is no medium or long-range order, but the first co-ordination sphere is well defined. As
2S
3 is a good glass former and exhibits a wide glass-forming region in its phase diagram.
From the elements
Amorphous As
2S
3 is obtained via the fusion of the elements at 390 °C. Rapid cooling of the reaction melt ensures the disordered arrangement of the bonds, resulting in the glass. Like other chemical syntheses, pure precursors and the exclusion of air provides purer product. The reaction can be represented with the chemical equation:
- 2 As + 3 S → As2S3
Upon heating in a vacuum, polymeric As
2S
3 "cracks" to give a mixture of molecular species, including molecular As
4S
6. As
4S
6 adopts the
adamantaneAdamantane is a colourless, crystalline compound with a camphor-like odour. With a formula C10H16, it is a cycloalkane and also the simplest diamondoid. Adamantane was discovered in petroleum in 1933. Its name derived from the Greek adamantinos , due to its diamond-like...
geometry, like that observed for P
4O
6 and As
4O
6. When a film of this material is exposed to an external energy source such as thermal energy (via thermal annealing ), electromagnetic radiation (i.e. UV lamps, lasers, electron beams)), As
4S
6 polymerizes:
- 2/n (As2S3)n As4S6
Aqueous precipitation
- See also: Qualitative inorganic analysis
Classical qualitative inorganic analysis is a method of analytical chemistry which seeks to find elemental composition of inorganic compounds. It is mainly focused on detecting ions in an aqueous solution, so that materials in other forms may need to be brought into this state before using standard...
As
2S
3 forms when aqueous solutions containing As(III) are treated with H
2S. Arsenic was in the past analyzed and assayed by this reaction, which results in the
precipitationPrecipitation is the formation of a solid in a solution during a chemical reaction. When the reaction occurs, the solid formed is called the precipitate, and the liquid remaining above the solid is called the supernate...
of As
2S
3, which is then weighed. As
2S
3 can even be precipitated in 6M HCl. As
2S
3 is so insoluble that it is not toxic. As
2S
3 characteristically dissolves upon treatment with aqueous solutions containing
sulfideA sulfide is a chemical compound containing sulfur in its lowest oxidation number of −2.- Properties :...
ions. The dissolved arsenic species is the pyramidal trianion AsS{{su|b=3|p=3−}}:
- As2S3 + 6 NaSH → 2 AsS{{su|b=3|p=3−}} + 3 H2S
As
2S
3 is the anhydride of the hypothetical thioarsenous acid, As(SH)
3. Upon treatment with
polysulfidePolysulfides are a class of chemical compounds containing chains of sulfur atoms. The two main classes of polysulfides are anions with the general formula Sn2−. These anions are the conjugate bases of the hydrogen polysulfides H2Sn...
ions, As
2S
3 dissolves to give a variety of species containing both S-S and As-S bonds. One of the more noteworthy derivatives is S
7As-S
-, a ring that contains an exocyclic sulfido center attached to the As atom. As
2S
3 also dissolves in strongly alkaline solutions to give a mixture of AsS{{su|b=3|p=3−}} and
AsO
{{chembox
| Name = Arsenic trisulfide
| ImageFile = Orpiment-unit-cell-3D.png
| ImageName = The unit cell of orpiment
| ImageFile1 = Orpiment_mineral.jpg
| ImageName1 = Orpiment, the mineral form of arsenic trisulfide
| OtherNames = Arsenic(III) sulfide
OrpimentOrpiment, As2S3, is a common monoclinic arsenic sulfide mineral. It has a Mohs hardness of 1.5 to 2 and a specific gravity of 3.46. It melts at 300 °C to 325 °C...
| Section1 = {{Chembox Identifiers
| CASNo = 1303-33-9
}}
| Section2 = {{Chembox Properties
| Formula = As
2S
3
| MolarMass = 246.041 g/mol
| Appearance = yellow-orange powder or crystals
| Density = 3.43 g/cm
3, solid
| Solubility = insoluble
| MeltingPt = 310 °C
| BoilingPt = 707 °C
}}
| Section7 = {{Chembox Hazards
| EUClass = not listed
| NFPA-H = 4
| NFPA-F =
| NFPA-R = 2
}}
| Section8 = {{Chembox Related
| OtherAnions = As
2O
3
| OtherCations = P
4S
6
| OtherCpds =
P4S10Phosphorus pentasulfide is the chemical compound with the formula P
4S
10. This yellow solid is an industrially important inorganic compound of phosphorus and sulfur. Commercial samples often appear greenish-gray. The compound has a low solubility in carbon disulfide and...
,
AsCl3Arsenic trichloride is the chemical compound with the formula AsCl3. The substance was known to alchemy under the name butter of arsenic.-Preparation:...
}}
}}
Arsenic trisulfide is the
chemical compoundA chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
with the formula
As2Arsenic is the chemical element that has the symbol As, atomic number 33 and atomic mass 74.92. Arsenic was first documented by Albertus Magnus in 1250. Arsenic is a notoriously poisonous metalloid with many allotropic forms, including a yellow and several black and grey forms...
S3Sulfur or sulphur is the chemical element that has the atomic number 16. It is denoted with the symbol S. It is an abundant, multivalent non-metal. Sulfur, in its native form, is a yellow crystalline solid. In nature, it can be found as the pure element and as sulfide and sulfate minerals...
. This bright yellow solid is well known because it occurs as the mineral
orpimentOrpiment, As2S3, is a common monoclinic arsenic sulfide mineral. It has a Mohs hardness of 1.5 to 2 and a specific gravity of 3.46. It melts at 300 °C to 325 °C...
(Latin: auripigment), has been used as a pigment, and has played a role in the analysis of arsenic compounds. This
chalcogenideA chalcogenide is a chemical compound consisting of at least one chalcogen ion and at least one more electropositive element. Although all group 16 elements of the periodic table are defined as chalcogens, the term is more commonly reserved for sulfides, selenides, and tellurides, rather than...
material is a group V/VI, intrinsic p-type, semiconductor and exhibits photo-induced phase-change properties.
The other important As-S phase is
realgarRealgar, α-As
4S
4, is an arsenic sulfide mineral. It is a soft, sectile mineral occurring in monoclinic crystals, or in granular, compact, or powdery form, often in association with the related mineral, orpiment . It is orange-red in colour, melts at 320 °C, and burns with a...
, As
4S
4, which is red-orange and also occurs as a mineral.
Structure
As
2S
3 occurs both in crystalline and amorphous forms. Both forms feature polymeric structures consisting As(III) centers are three-fold co-ordinated by sulfide centres in a
trigonal pyramidIn chemistry, a trigonal pyramid is a molecular geometry with one atom at the apex and three atoms at the corners of a trigonal base. When all three atoms at the corners are identical, the molecule belongs to point group C3v. One example of a molecule with a trigonal pyramidal geometry...
al geometery. The sulfide centres are two-fold coordinated to two arsenic atoms. In the crystalline form, the As-S bonds form bonded sheets. The bonding between the sheets consists of van der Waals forces. The crystalline form is usually found in geological samples. Amorphous As
2S
3 does not possess a layered structure but is more highly cross-linked. Like other glasses, there is no medium or long-range order, but the first co-ordination sphere is well defined. As
2S
3 is a good glass former and exhibits a wide glass-forming region in its phase diagram.
From the elements
Amorphous As
2S
3 is obtained via the fusion of the elements at 390 °C. Rapid cooling of the reaction melt ensures the disordered arrangement of the bonds, resulting in the glass. Like other chemical syntheses, pure precursors and the exclusion of air provides purer product. The reaction can be represented with the chemical equation:
- 2 As + 3 S → As2S3
Upon heating in a vacuum, polymeric As
2S
3 "cracks" to give a mixture of molecular species, including molecular As
4S
6. As
4S
6 adopts the
adamantaneAdamantane is a colourless, crystalline compound with a camphor-like odour. With a formula C10H16, it is a cycloalkane and also the simplest diamondoid. Adamantane was discovered in petroleum in 1933. Its name derived from the Greek adamantinos , due to its diamond-like...
geometry, like that observed for P
4O
6 and As
4O
6. When a film of this material is exposed to an external energy source such as thermal energy (via thermal annealing ), electromagnetic radiation (i.e. UV lamps, lasers, electron beams)), As
4S
6 polymerizes:
- 2/n (As2S3)n As4S6
Aqueous precipitation
- See also: Qualitative inorganic analysis
Classical qualitative inorganic analysis is a method of analytical chemistry which seeks to find elemental composition of inorganic compounds. It is mainly focused on detecting ions in an aqueous solution, so that materials in other forms may need to be brought into this state before using standard...
As
2S
3 forms when aqueous solutions containing As(III) are treated with H
2S. Arsenic was in the past analyzed and assayed by this reaction, which results in the
precipitationPrecipitation is the formation of a solid in a solution during a chemical reaction. When the reaction occurs, the solid formed is called the precipitate, and the liquid remaining above the solid is called the supernate...
of As
2S
3, which is then weighed. As
2S
3 can even be precipitated in 6M HCl. As
2S
3 is so insoluble that it is not toxic. As
2S
3 characteristically dissolves upon treatment with aqueous solutions containing
sulfideA sulfide is a chemical compound containing sulfur in its lowest oxidation number of −2.- Properties :...
ions. The dissolved arsenic species is the pyramidal trianion AsS{{su|b=3|p=3−}}:
- As2S3 + 6 NaSH → 2 AsS{{su|b=3|p=3−}} + 3 H2S
As
2S
3 is the anhydride of the hypothetical thioarsenous acid, As(SH)
3. Upon treatment with
polysulfidePolysulfides are a class of chemical compounds containing chains of sulfur atoms. The two main classes of polysulfides are anions with the general formula Sn2−. These anions are the conjugate bases of the hydrogen polysulfides H2Sn...
ions, As
2S
3 dissolves to give a variety of species containing both S-S and As-S bonds. One of the more noteworthy derivatives is S
7As-S
-, a ring that contains an exocyclic sulfido center attached to the As atom. As
2S
3 also dissolves in strongly alkaline solutions to give a mixture of AsS{{su|b=3|p=3−}} and
AsO{{suIn chemistry an arsenite is a chemical compound containing an arsenic oxoanion where arsenic has oxidation state +3. Examples of arsenites include sodium arsenite which contains a polymeric linear anion, [AsO2−]n, silver arsenite, Ag3AsO3,...
.
Reactions with oxygen
"Roasting" As
2S
3 in air gives volatile, toxic derivatives, this conversion being one of the hazards associated with the refining of heavy metal
oreAn ore is a type of rock that contains minerals such as gemstones or metals that can be extracted through mining and refined for use. Samples of ore in the form of exceptionally beautiful crystals, exotic layering visible when sectioned or polished or metallic presentations such as large nuggets or...
s:
- 2 As2S3 + 9 O2 → As4O6 + 6 SO2
As an inorganic photoresist
Due to its high
refractive indexThe refractive index of a medium is a measure of how much the speed of light is reduced inside the medium. For example, typical soda-lime glass has a refractive index close to 1.5, which means that in glass, light travels at 1 / 1.5 = 2/3 the speed of light in a vacuum...
of 2.45 and its large
Knoop hardnessThe Knoop hardness test is a microhardness test - a test for mechanical hardness used particularly for very brittle materials or thin sheets, where only a small indentation may be made for testing purposes...
compared to organic
photoresistA photoresist is a light-sensitive material used in several industrial processes, such as photolithography and photoengraving to form a patterned coating on a surface.-Tone:Photoresists are classified into two groups: positive resists and negative resists....
s, As
2S
3 has been investigated for the fabrication of
photonic crystalPhotonic crystals are periodic optical nanostructures that are designed to affect the motion of photons in a similar way that periodicity of a semiconductor crystal affects the motion of electrons...
s with a full-photonic band-gap. Advances in laser patterning techniques such as three-dimensional direct laser writing (3-D DLW) and chemical wet-
etching chemistryEtching is used in microfabrication to chemically remove layers from the surface of a wafer during manufacturing. Etching is a critically important process module, and every wafer undergoes many etching steps before it is complete....
, has allowed this material to be used as a photoresist to fabricate 3-D nanostructures.
As
2S
3 has been investigated for use as a high resolution photoreist material since the early 1970s, using aqueous etchants. Although these aqueous etchants allowed for low-aspect ratio 2-D structures to be fabricated, they do not allow for the etching of high aspect ratio structures with 3-D periodicity. Certain organic reagents, used in organic solvents, permit the high-etch selectivity required to produce high-aspect ratio structures with 3-D periodicity.
Medical applications
As
2S
3 and As
4S
4 have been investigated as treatments for acute promyelocytic leukemia (APL). The mode of action is thought to be similar to that for
As2O3Arsenic trioxide is the inorganic compound with the formula As2O3. This commercially important oxide of arsenic is the main precursor to other arsenic compounds, including organoarsenic compounds. Approximately 50,000 tons are produced annually...
.
For IR-transmitting glasses
Arsenic trisulfide manufactured into amorphous form is used as a
chalcogenide glassA chalcogenide glass is a glass containing one or more chalcogenide elements as a substantial constituent...
for
infraredInfrared radiation is electromagnetic radiation whose wavelength is longer than that of visible light , but shorter than that of terahertz radiation and microwaves...
opticsOptics is the branch of physics which studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light...
. It is transparent between 620 nm and 11 µm. The arsenic trisulfide glass is more resistant to oxidation than crystalline arsenic trisulfide, which minimizes toxicity concerns. It can be also used as an acousto-optic material.
Role in ancient artistry
{{main|orpiment}}
The ancient Egyptians reportedly used orpiment, natural or synthetic, as a pigment in artistry and cosmetics.
Miscellaneous
Arsenic trisulfide is also used as a
tanningTanning is the process of making leather, which does not easily decompose, from the skins of animals, which do. Often this uses tannin, an acidic chemical compound. Coloring may occur during tanning....
agent. It was formerly used with
indigo dyeIndigo dye is an organic compound with a distinctive blue color . Historically, indigo was extracted from plants, and this process was important economically because blue dyes were once rare. Nearly all indigo produced today - several thousand tons each year - is synthetic...
for the production of pencil blue, which allowed dark blue hues to be added to fabric via pencil or brush.
Precipitation of arsenic trisulfide is used as an analytical test for presence of dissimilatory arsenic-reducing bacteria (DARB).
Safety
As
2S
3 is so insoluble that it is considered non-toxic. Crystalline As
2S
3 however tends to oxidize on the surface, forming a layer of toxic
arsenic trioxideArsenic trioxide is the inorganic compound with the formula As2O3. This commercially important oxide of arsenic is the main precursor to other arsenic compounds, including organoarsenic compounds. Approximately 50,000 tons are produced annually...
. Commercial orpiment can however contain substantial amounts of arsenic oxides, which are soluble and therefore highly toxic.
Natural occurrence
Orpiment is found in volcanic environments, often together with other arsenic sulfides, mainly
realgarRealgar, α-As
4S
4, is an arsenic sulfide mineral. It is a soft, sectile mineral occurring in monoclinic crystals, or in granular, compact, or powdery form, often in association with the related mineral, orpiment . It is orange-red in colour, melts at 320 °C, and burns with a...
. It is sometimes found in low-temperature hydrothermal veins, together with some other sulfide and sulfosalt minerals.