spore: profile
id: arsenic-trisulfide
spore_version: 0.2
family: chalcogenide-glass
name: Arsenic trisulfide
abbreviation: As2S3
role: infrared optical glass
category: glasses-optics
type: optical-crystals
summary: Arsenic trisulfide (As2S3) is an arsenic-sulfur chalcogenide glass that transmits infrared light from about 620 nm to 11 µm, according to a UCF/CREOL paper. AZoM lists its density as 3.46 g/cm3 and its melting point as 310 °C. The supplier safety data sheet classifies the powder as toxic if swallowed or if inhaled, so it is an infrared optics material that needs strict handling.
best_for: Infrared windows and laser-written micro-structures, where the infrared window matters more than low toxicity
weakest_at: 'Toxicity: the arsenic content makes it a hazardous material to handle, store and dispose of'
identity:
  formula: As2S3
  cas: 1303-33-9
  crystal_system: monoclinic
  source: azom-as2s3
  where: Chemical Properties table (Chemical Formula, CAS No. and Crystal Structure rows)
tags:
  environments: []
  stresses: []
  applications:
    - optics-and-cameras
properties:
  - benchmark: density
    value: 3.46
    unit: g/cm3
    scope: material
    conditions:
      basis: no temperature, form or test condition printed on the page
    method: Value printed in the Mechanical Properties table of the AZoM article
    status: ground
    note: Apollo Scientific also prints 3.43 g/cm3 (recorded below). Wikipedia's 3.43 g/cm3 is not recorded (see gaps).
    source: azom-as2s3
    where: Mechanical Properties table, Density row
  - benchmark: density
    value: 3.43
    unit: g/cm3
    scope: material
    conditions:
      basis: product page for Apollo Scientific catalogue IN1166 (99.999%); no temperature printed
    method: Value printed in the physical data section of the Apollo Scientific product page
    status: ground
    note: Differs from the AZoM value of 3.46 g/cm3 (see gaps).
    source: apollo-as2s3
    where: Physical data, Density
  - benchmark: melting_point
    value: 310
    unit: °C
    scope: material
    conditions:
      basis: no condition printed on the page
    method: Value printed in the Mechanical Properties table of the AZoM article
    status: ground
    source: azom-as2s3
    where: Mechanical Properties table, Melting Point row
  - benchmark: melting_point
    value: 300
    unit: °C
    scope: material
    conditions:
      basis: product page for Apollo Scientific catalogue IN1166 (99.999%); no condition printed
    method: Value printed in the physical data section of the Apollo Scientific product page
    status: ground
    note: Differs from the AZoM value of 310 °C (see gaps).
    source: apollo-as2s3
    where: Physical data, Melting point
  - benchmark: boiling_point
    value: 707
    unit: °C
    scope: material
    conditions:
      basis: no condition printed on the page
    method: Value printed in the Mechanical Properties table of the AZoM article
    status: ground
    source: azom-as2s3
    where: Mechanical Properties table, Boiling Point row
  - benchmark: refractive_index
    value: 2.4
    unit: '-'
    scope: material
    conditions:
      wavelength: not printed on the page
    method: Value printed in the Optical Properties table of the AZoM article
    status: ground
    note: The page gives no wavelength. Wikipedia gives 2.45 with no condition; the two disagree (see gaps).
    source: azom-as2s3
    where: Optical Properties table, Refractive Index row
  - benchmark: mohs_hardness
    value: 1.8
    unit: '-'
    scope: material
    conditions:
      scale: Mohs scale, a dimensionless ranking; no unit printed
    method: Value printed in the Mechanical Properties table of the AZoM article
    status: ground
    source: azom-as2s3
    where: Mechanical Properties table, Mohs Hardness row
  - benchmark: molar_heat_capacity
    value: 116.3
    unit: J/mol K
    scope: material
    conditions:
      basis: printed as Specific Heat Capacity in molar units; not converted to per kilogram
    method: Value printed in the Thermal Properties table of the AZoM article
    status: ground
    source: azom-as2s3
    where: Thermal Properties table, Specific Heat Capacity row
  - benchmark: standard_molar_entropy
    value: 163.6
    unit: J/mol K
    scope: material
    conditions:
      basis: standard molar entropy as printed; no reference temperature stated
    method: Value printed in the Thermal Properties table of the AZoM article
    status: ground
    source: azom-as2s3
    where: Thermal Properties table, Standard molar entropy row
  - benchmark: heat_of_formation
    value: -169
    unit: kJ/mol
    scope: material
    conditions:
      basis: no reference state or temperature printed on the page
    method: Value printed in the Thermal Properties table of the AZoM article
    status: ground
    source: azom-as2s3
    where: Thermal Properties table, Heat of Formation row
  - benchmark: lattice_constant_a
    value: 11.49
    unit: Å
    scope: material
    conditions:
      crystal_system: monoclinic
      temperature: not printed on the page
    method: Value printed in the Chemical Properties table of the AZoM article
    status: ground
    source: azom-as2s3
    where: Chemical Properties table, Lattice Constant row (a)
  - benchmark: lattice_constant_b
    value: 9.59
    unit: Å
    scope: material
    conditions:
      crystal_system: monoclinic
      temperature: not printed on the page
    method: Value printed in the Chemical Properties table of the AZoM article
    status: ground
    source: azom-as2s3
    where: Chemical Properties table, Lattice Constant row (b)
  - benchmark: lattice_constant_c
    value: 4.25
    unit: Å
    scope: material
    conditions:
      crystal_system: monoclinic
      temperature: not printed on the page
    method: Value printed in the Chemical Properties table of the AZoM article
    status: ground
    source: azom-as2s3
    where: Chemical Properties table, Lattice Constant row (c)
  - benchmark: molecular_weight
    value: 246
    unit: g/mol
    scope: material
    conditions:
      basis: computed by PubChem 2.1, not measured
    method: Computed value printed in the PubChem record for CID 4093503 (Molecular Weight section)
    status: calculated
    source: pubchem-as2s3
    where: Molecular Weight section of the PubChem record (CID 4093503)
  - benchmark: ir_transmission_lower_wavelength
    label: Shortest wavelength transmitted (infrared window, lower limit)
    value: 620
    unit: nm
    bound: lower
    scope: material
    conditions:
      basis: stated as approximately 620 nm in the paper
      material: As2S3 glass as described in the paper; bulk and film not separated
    method: Value stated in the abstract and introduction of the UCF/CREOL paper
    status: ground
    source: ucf-as2s3
    where: Abstract; Section 1 (Introduction), first paragraph
  - benchmark: ir_transmission_upper_wavelength
    label: Longest wavelength transmitted (infrared window, upper limit)
    value: 11
    unit: µm
    bound: upper
    scope: material
    conditions:
      basis: stated as the upper end of the infrared transparency range
      material: As2S3 glass as described in the paper
    method: Value stated in the abstract and introduction of the UCF/CREOL paper
    status: ground
    source: ucf-as2s3
    where: Abstract; Section 1 (Introduction), first paragraph
  - benchmark: ld50_oral_rat
    label: Acute oral LD50, rat
    value: 185
    unit: mg/kg
    scope: material
    conditions:
      species: rat
      route: oral
      product: arsenic sulfide (As2S3) powder, per the supplier SDS
    method: Acute oral LD50 printed in the toxicological information section of the supplier SDS
    status: ground
    source: samaterials-sds
    where: Section 11, Acute toxicity (LD/LC50 values relevant for classification)
  - benchmark: ld50_dermal_rat
    label: Acute dermal LD50, rat
    value: 936
    unit: mg/kg
    scope: material
    conditions:
      species: rat
      route: dermal
      product: arsenic sulfide (As2S3) powder, per the supplier SDS
    method: Acute dermal LD50 printed in the toxicological information section of the supplier SDS
    status: ground
    source: samaterials-sds
    where: Section 11, Acute toxicity (LD/LC50 values relevant for classification)
corrosion:
  - environment: Air, oxidation of the glass
    headline: The glass form resists oxidation better than the crystalline form, according to Wikipedia.
    effect: Wikipedia states that the arsenic trisulfide glass is more resistant to oxidation than crystalline arsenic trisulfide, which minimizes toxicity concerns. The page gives no oxidation rate, humidity or temperature for this statement.
    rating: low
    conditions:
      basis: qualitative statement only; no test conditions printed
    source: wikipedia-as2s3
    where: Section on IR-transmitting glasses
  - environment: Aged samples of the material
    headline: Aged samples can contain soluble arsenic oxides, which Wikipedia calls highly toxic.
    effect: Wikipedia states that aged samples can contain substantial amounts of arsenic oxides, which are soluble and therefore highly toxic. No ageing time, temperature or humidity is given.
    rating: moderate
    conditions:
      basis: qualitative statement only; no ageing conditions printed
    source: wikipedia-as2s3
    where: Safety section
risks:
  hazards:
    - text: 'Supplier SDS for arsenic sulfide (As2S3) powder: signal word Danger, pictogram GHS06, hazard statements H301 (toxic if swallowed) and H331 (toxic if inhaled).'
      ghs:
        - H301
        - H331
      source: samaterials-sds
      where: Section 2, GHS label elements
    - text: AZoM lists H301 (toxic if swallowed), H331 (toxic if inhaled) and H410 (very toxic to aquatic life with long lasting effects) for arsenic trisulfide.
      ghs:
        - H301
        - H331
        - H410
      source: azom-as2s3
      where: Safety Information, GHS Hazard Statements list
    - text: Apollo Scientific (catalogue IN1166) lists H330 (fatal if inhaled) and H301+H311 (toxic if swallowed or in contact with skin), with a GHS06 pictogram. Its H330 differs from H331 (toxic if inhaled) in the SDS and AZoM; both are kept.
      ghs:
        - H330
        - H301
        - H311
      source: apollo-as2s3
      where: Product page, hazard statements and pictogram
    - text: 'The supplier SDS prints carcinogen classifications for this material: IARC-1 (carcinogenic to humans), ACGIH A1 (confirmed human carcinogen) and NTP-K (known to be carcinogenic).'
      ghs: []
      source: samaterials-sds
      where: Section 11, Carcinogenicity
  failure_risks:
    - mode: Delamination from thermal expansion (chalcogenide glasses in general)
      trigger: Temperature change on a bonded or constrained component
      consequence: The UCF/CREOL paper says a high coefficient of thermal expansion can cause component failure through delamination, so temperature control becomes necessary. The paper is about chalcogenide glasses in general and gives no expansion value for As2S3.
      severity: moderate
      source: ucf-as2s3
      where: Section 1 (Introduction), second paragraph
    - mode: Release of soluble arsenic oxides from aged samples
      trigger: Storage or ageing of the material
      consequence: Soluble arsenic oxides, which Wikipedia calls highly toxic, can be present in aged samples.
      severity: high
      source: wikipedia-as2s3
      where: Safety section
  side_effects:
    - text: The supplier SDS lists arsenic oxides, toxic metal oxide fume, sulfur oxides and hydrogen sulfide as hazardous decomposition products.
      affects: People near a fire or during overheating
      source: samaterials-sds
      where: Section 10, Hazardous decomposition products
  handling:
    - text: 'AZoM precautions: avoid breathing dust, fume, gas, mist, vapours or spray (P261); avoid release to the environment (P273); dispose of contents and container at an approved waste disposal plant (P501).'
      source: azom-as2s3
      where: Safety Precautions list
    - text: 'NIOSH pocket guide entry for arsenic, inorganic compounds (as As), which Wikipedia cites for this material: OSHA PEL printed as [1910.1018] TWA 0.010 mg/m3; NIOSH REL printed as Ca C 0.002 mg/m3 [15-minute]; IDLH printed as Ca [5 mg/m3 (as As)].'
      source: niosh-npg-0038
      where: Exposure limits, PEL, REL and IDLH rows
uses:
  - application: optics-and-cameras
    device: Infrared-transmitting glass for optics and sensors
    example: The UCF/CREOL paper describes As2S3 as an infrared transparent material with direct applications in IR sensors, photonic waveguides and acousto-optics.
    source: ucf-as2s3
    where: Abstract; Section 1 (Introduction)
  - application: optics-and-cameras
    device: Photoresist for laser-written three-dimensional micro-structures (laboratory use)
    example: The UCF/CREOL paper reports that thermally deposited As2S3 films can be photo-patterned like polymeric photoresists, and that woodpile photonic crystals, nanowires and waveguides have been fabricated in As2S3 by direct laser writing.
    source: ucf-as2s3
    where: Section 1 (Introduction)
  - application: optics-and-cameras
    device: Infrared seeker nose cone of the de Havilland Firestreak missile (historic)
    example: Wikipedia records that arsenic trisulfide was used for the eight-sided conical nose over the infrared seeker of the de Havilland Firestreak missile.
    source: wikipedia-as2s3
    where: History section (Contemporary uses, IR-transmitting glasses)
supply:
  - subject: Arsenic (as arsenic trioxide, the arsenic product USGS reports; As2S3 itself is not reported separately)
    producers:
      - country: Peru
        share_percent: 49.2
        year: 2025
      - country: China
        share_percent: 39.3
        year: 2025
      - country: Morocco
        share_percent: 8.2
        year: 2025
      - country: Belgium
        share_percent: 1.6
        year: 2025
      - country: Russia
        share_percent: 0.8
        year: 2025
    recycling: 'USGS: arsenic metal was contained in new scrap recycled during GaAs semiconductor manufacturing, and no arsenic was known to have been recovered from scrap electronic circuit boards, relays and switches.'
    substitutes: []
    source: usgs-mcs2026-arsenic
    where: World Production and Capacity table, 2025 column of production (arsenic trioxide, gross weight); shares calculated by Space Mushroom against the printed world total of 61,000; Recycling section
documents:
  - title: 'Safety data sheet: arsenic sulfide (As2S3) powder (supplier SDS)'
    type: sds
    url: https://samaterials.com/tds/1697118961-2645-arsenic-sulfide-as2s3-powder-sds.pdf
  - title: Processing and properties of arsenic trisulfide chalcogenide glasses for direct laser writing of 3D micro-structures (UCF/CREOL, open PDF)
    type: paper
    url: https://api.creol.ucf.edu/Publications/7446.pdf
  - title: 'Mineral Commodity Summaries 2026: Arsenic (USGS)'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-arsenic.pdf
    year: 2026
  - title: 'PubChem compound record: Arsenic (III) sulfide (CID 4093503)'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/4093503
    year: 2026
gaps:
  - No flight, vacuum, radiation or space-environment result for arsenic trisulfide was found, and no space application source was read.
  - No glass transition temperature and no coefficient of thermal expansion for As2S3 was found in a source we could open. The UCF/CREOL paper's expansion statement is qualitative and about chalcogenide glasses in general.
  - Band gap of 2.7 eV (direct) is printed only in Wikipedia, which this profile uses for composition, history and qualitative statements. It is not recorded as a property.
  - 'Density: AZoM gives 3.46 g/cm3 and Apollo Scientific gives 3.43 g/cm3; both are recorded side by side. Wikipedia gives 3.43 g/cm3 at standard state (25 °C and 100 kPa) and refractive index 2.45 with no condition; the Wikipedia values are not recorded as properties.'
  - 'Melting point: AZoM gives 310 °C and Apollo Scientific gives 300 °C; both are recorded side by side.'
  - 'Inhalation hazard code: Apollo Scientific lists H330 (fatal if inhaled); the SDS and AZoM list H331 (toxic if inhaled). Both are kept in the hazard list.'
  - The AZoM refractive index has no wavelength. A bulk-glass refractive index at a stated wavelength was not found in a source we could open; the Knotek et al. 2020 paper and the Makovetsky article could not be opened.
  - Magnetic susceptibility is printed with an exponent in Wikipedia and without a unit in AZoM, so it is not recorded.
  - No trade name, AMTIR designation or grade code is printed in the sources read. The lane note mentions AMTIR-6, but no source read here names it for this material, so no designation is listed.
  - Fibre drawing, moulding and processing temperatures for As2S3 were not found in the sources read.
  - Crustal abundance of arsenic was not found in a source we could open.
  - The USGS arsenic chapter read here does not state whether arsenic is on the USGS or EU critical-mineral lists, so no list status is recorded.
  - The USGS production data cover arsenic trioxide, not As2S3. Producer shares are calculated from printed tonnages.
  - PubChem's GHS classification page was blocked in this run (reCAPTCHA), so no PubChem hazard codes are recorded. Wikipedia also lists H300, H400 and H411, which the supplier SDS, AZoM and Apollo Scientific do not print; they are not recorded as hazards.
  - NIOSH exposure limits are for arsenic, inorganic compounds (as As), not separately for As2S3.
  - Element atomic weights for arsenic and sulfur were not taken from a fetched source, so the recipe gives atom counts only.
  - Taxonomy has no chalcogenide type. optical-crystals is the nearest infrared-optics slug.
  - 'Non-canonical benchmark names used: molar_heat_capacity, standard_molar_entropy, heat_of_formation, mohs_hardness, lattice_constant_a, lattice_constant_b, lattice_constant_c, molecular_weight, ir_transmission_lower_wavelength, ir_transmission_upper_wavelength, ld50_oral_rat and ld50_dermal_rat.'
sources:
  azom-as2s3:
    title: Arsenic trisulfide, AZoM materials article (ArticleID 8438)
    id: AZoM ArticleID 8438
    url: https://www.azom.com/article.aspx?ArticleID=8438
    kind: web
    license: AZoM article, cited not reproduced
  wikipedia-as2s3:
    title: Arsenic trisulfide (Wikipedia)
    id: Wikipedia, Arsenic trisulfide
    url: https://en.wikipedia.org/wiki/Arsenic_trisulfide
    kind: web
    license: CC BY-SA 4.0 (Wikipedia text)
  ucf-as2s3:
    title: Processing and properties of arsenic trisulfide chalcogenide glasses for direct laser writing of 3D micro-structures
    id: Schwarz, Williams, Grabill, Lewis, Kuebler et al., University of Central Florida (CREOL)
    url: https://api.creol.ucf.edu/Publications/7446.pdf
    kind: paper
    license: open PDF; licence not stated on the document
  usgs-mcs2026-arsenic:
    title: 'Mineral Commodity Summaries 2026: Arsenic'
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-arsenic.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  pubchem-as2s3:
    title: PubChem compound record, Arsenic (III) sulfide (CID 4093503), JSON view
    id: CID 4093503; CAS 1303-33-9
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/4093503/JSON
    year: 2026
    kind: database
    license: public domain (NCBI)
  samaterials-sds:
    title: 'Safety data sheet: arsenic sulfide (As2S3) powder (supplier SDS)'
    id: Supplier SDS, product file 1697118961-2645
    url: https://samaterials.com/tds/1697118961-2645-arsenic-sulfide-as2s3-powder-sds.pdf
    kind: datasheet
    license: supplier document, linked not reproduced
  apollo-as2s3:
    title: Arsenic(III) sulfide, 99.999%, catalogue IN1166 (Apollo Scientific product page)
    id: Apollo Scientific catalogue IN1166; CAS 1303-33-9
    url: https://store.apolloscientific.co.uk/product/arseniciii-sulfide
    kind: datasheet
    license: supplier product page, cited not reproduced
  niosh-npg-0038:
    title: 'NIOSH Pocket Guide to Chemical Hazards: Arsenic, inorganic compounds (as As)'
    id: NIOSH NPG entry 0038 (page reviewed 30 October 2019)
    url: https://www.cdc.gov/niosh/npg/npgd0038.html
    year: 2019
    kind: handbook
    license: public domain (US government)
license: CC-BY-4.0
updated: '2026-11-01'
review:
  status: draft
  method: assistant
  checked_values: 18
  unreachable: 6
  caveats: 3
  note: 'Read by an AI assistant on 2026-11-01. Eight sources were read. Candidate sources that could not be opened from this environment: ECHA (HTTP 403), DTIC, Springer (login redirect), RSC Advances (HTTP 403), the Makovetsky article and the JOAM PDFs.'
story:
  recipe:
    line: 'Arsenic trisulfide is As2S3: two arsenic atoms and three sulfur atoms per formula unit. The UCF/CREOL paper describes thin films deposited by thermal evaporation of the bulk glass.'
    parts:
      - name: Arsenic
        symbol: As
        role: The heavy element that gives the glass its high refractive index and its toxicity.
      - name: Sulfur
        symbol: S
        role: The network former that bonds to arsenic and holds the glass together.
  risk_groups:
    - title: For people
      level: 0
      verdict: Toxic if swallowed or inhaled
      lead: The supplier SDS classifies the powder as toxic if swallowed or inhaled and prints carcinogen classifications for it.
      points:
        - label: Swallowed or inhaled
          line: The supplier SDS lists H301 (toxic if swallowed) and H331 (toxic if inhaled). Apollo Scientific lists H330 (fatal if inhaled) for the same compound.
        - label: Cancer classification
          line: The SDS prints IARC-1 (carcinogenic to humans) and ACGIH A1 (confirmed human carcinogen).
        - label: Dust and fume
          line: AZoM advises avoiding breathing dust, fume, gas, mist, vapours or spray (P261).
    - title: If the material ages or burns
      verdict: Aged samples can release arsenic oxides
      lead: These statements are qualitative. The sources do not give ageing or heating conditions.
      points:
        - label: Aged samples
          line: Wikipedia says aged samples can contain soluble arsenic oxides, which it calls highly toxic.
        - label: Fire
          line: The SDS lists arsenic oxides, sulfur oxides and hydrogen sulfide as hazardous decomposition products.
    - title: Handling and storage
      verdict: Follow the arsenic exposure limits
      lead: The exposure limits below are for arsenic, inorganic compounds (as As), which the NIOSH pocket guide covers.
      points:
        - label: Exposure limits
          line: The OSHA PEL is 0.010 mg/m3 as a TWA, and the NIOSH REL is Ca C 0.002 mg/m3 over 15 minutes.
        - label: Environment
          line: Avoid release to the environment (P273) and send waste to an approved disposal plant (P501).
  why: Arsenic trisulfide (As2S3) is a chalcogenide glass that transmits infrared light from about 620 nm to 11 µm, according to a UCF/CREOL paper. Designers use that window for infrared sensors and laser-written photonic structures. The same arsenic chemistry makes the material toxic, so every use comes with handling limits.
  uses:
    - where: Infrared optics and sensors
      line: A UCF/CREOL paper describes As2S3 as an infrared transparent material with direct applications in IR sensors, photonic waveguides and acousto-optics.
    - where: Photoresist for laser-written micro-structures
      line: The same paper reports that As2S3 films can be patterned by laser like polymeric photoresists, and that woodpile photonic crystals, nanowires and waveguides have been made in it by direct laser writing.
    - where: A historic missile nose cone
      line: Wikipedia records that arsenic trisulfide was used for the eight-sided conical nose over the infrared seeker of the de Havilland Firestreak missile.
  can_do:
    - label: Infrared transmission
      line: Transmits infrared light from about 620 nm to 11 µm, according to the UCF/CREOL paper.
    - label: Density
      benchmark: density
      line: AZoM lists a density of 3.46 g/cm3, with no temperature printed.
    - label: Melting point
      benchmark: melting_point
      line: AZoM lists a melting point of 310 °C.
    - label: Acute toxicity
      benchmark: ld50_oral_rat
      line: The supplier SDS gives an oral LD50 of 185 mg/kg in rats, which is why the powder is toxic if swallowed.
  compare: 'Arsenic trisulfide is an infrared glass like the other optical materials in this group, but its chemistry is different: it is an arsenic sulfide, not an oxide. Wikipedia states that the glass form resists oxidation better than the crystalline form. The table sets its density, melting point and refractive index side by side.'
  compare_rows:
    - label: Density
      benchmark: density
    - label: Melting point
      benchmark: melting_point
    - label: Refractive index
      benchmark: refractive_index
  handling:
    - Keep dust and fume out of the air. AZoM's precautions say to avoid breathing dust, fume, gas, mist, vapours or spray.
    - The NIOSH limits for arsenic, inorganic compounds (as As) are 0.010 mg/m3 for the OSHA PEL and 0.002 mg/m3 as the 15-minute NIOSH REL.
    - Keep the material out of the environment, and send waste to an approved disposal plant.
  good_for:
    - Infrared windows and sensors that need transmission from about 620 nm to 11 µm (UCF/CREOL paper).
    - Laser-written micro-structures, where As2S3 films act as an inorganic photoresist (UCF/CREOL paper).
  watch_out:
    - 'Toxic if swallowed or inhaled (SDS: H301 and H331). AZoM also lists H410, very toxic to aquatic life.'
    - Aged samples can contain soluble arsenic oxides, which Wikipedia calls highly toxic.
    - 'Sources disagree on the inhalation hazard code: H330 (fatal if inhaled) on the Apollo Scientific page, and H331 (toxic if inhaled) in the SDS and AZoM. Both are kept.'
  verdict: Arsenic trisulfide is a useful infrared glass for optics and laser-written micro-structures, but its arsenic content makes it a hazardous material that needs strict handling.