Arsenic As

spore: profile
id: arsenic
spore_version: 0.2
family: semiconductor-materials
name: Arsenic
abbreviation: As
role: 'Metalloid: feedstock for gallium arsenide semiconductors and a dopant'
category: semiconductors
type: silicon
summary: Arsenic is the element As, a metalloid. WebElements gives its solid density as 5727 kg/m3, its melting point as 817 °C under pressure, and says it sublimes at 614 °C. In the United States its leading use was herbicides, insecticides and wood preservatives (USGS), but high-purity arsenic metal (99.9999%) is made into gallium arsenide and indium gallium arsenide semiconductors for satellites, solar cells and wireless devices. PubChem reports the element as toxic if swallowed or inhaled.
best_for: Source of high-purity arsenic metal for GaAs and InGaAs semiconductors and for specialty infrared optics (USGS)
weakest_at: 'Toxicity: PubChem reports H301 and H331 for most reporting companies, and ATSDR classes inorganic arsenic as a known human carcinogen'
identity:
  formula: As, elemental arsenic, trigonal crystal (space group R-3m)
  crystal_system: trigonal
  space_group: R-3m
  source: we-crystal
  where: Crystal structures page, Space group row (R-3m, space group number 166); PubChem CID 5359596 for the element record
tags:
  environments: []
  stresses: []
  applications:
    - electronics-and-chips
    - solar-arrays
    - optics-and-cameras
properties:
  - benchmark: density
    label: Density of the solid
    value: 5727
    unit: kg/m3
    scope: material
    conditions:
      temperature: not stated on the page
    method: Value printed on the WebElements physics page (printed as 5727 kg m-3)
    status: ground
    source: we-physics
    where: Physics page, Density properties, Density of solid row
  - benchmark: elastic_modulus
    label: Young's modulus
    value: 8
    unit: GPa
    scope: material
    conditions:
      temperature: not stated on the page
    method: Value printed on the WebElements physics page
    status: ground
    source: we-physics
    where: Physics page, Elastic properties, Young's modulus row
  - benchmark: bulk_modulus
    label: Bulk modulus
    value: 22
    unit: GPa
    scope: material
    conditions:
      temperature: not stated on the page
    method: Value printed on the WebElements physics page
    status: ground
    source: we-physics
    where: Physics page, Elastic properties, Bulk modulus row
  - benchmark: thermal_conductivity
    label: Thermal conductivity
    value: 50
    unit: W m-1 K-1
    scope: material
    conditions:
      temperature: not stated on the page
    method: Value printed on the WebElements physics page
    status: ground
    source: we-physics
    where: Physics page, Heat and conduction, Thermal conductivity row
  - benchmark: melting_point
    label: Melting point under pressure
    value: 817
    unit: °C
    scope: material
    conditions:
      pressure: under pressure, value not stated on the page
      basis: printed as 1090 K with 817 °C in brackets
    method: Value printed on the WebElements thermochemistry page
    status: ground
    note: WebElements gives no liquid phase at normal pressure, so this is not an ambient-pressure melting point.
    source: we-thermochemistry
    where: Thermochemistry page, Melting point row
  - benchmark: boiling_point
    label: Sublimation point (printed as boiling point)
    value: 614
    unit: °C
    scope: material
    conditions:
      basis: printed as 887 K with 614 °C in brackets and the note (sublimes)
      pressure: not stated on the page
    method: Value printed on the WebElements thermochemistry page with the note (sublimes)
    status: ground
    source: we-thermochemistry
    where: Thermochemistry page, Boiling point row
  - benchmark: enthalpy_of_fusion
    label: Enthalpy of fusion
    value: 27.7
    unit: kJ/mol
    scope: material
    conditions:
      basis: as printed on the page; no temperature stated
    method: Value printed on the WebElements thermochemistry page
    status: ground
    source: we-thermochemistry
    where: Thermochemistry page, Enthalpies, Enthalpy of fusion row
  - benchmark: enthalpy_of_sublimation
    label: Enthalpy of sublimation
    value: 32.4
    unit: kJ/mol
    scope: material
    conditions:
      basis: printed as enthalpy of vaporisation with the note (sublimation)
    method: Value printed on the WebElements thermochemistry page
    status: ground
    source: we-thermochemistry
    where: Thermochemistry page, Enthalpies, Enthalpy of vaporisation row
  - benchmark: enthalpy_of_atomisation
    label: Enthalpy of atomisation
    value: 302
    unit: kJ/mol
    scope: material
    conditions:
      basis: as printed on the page
    method: Value printed on the WebElements thermochemistry page
    status: ground
    source: we-thermochemistry
    where: Thermochemistry page, Enthalpies, Enthalpy of atomisation row
  - benchmark: lattice_constant
    label: Lattice parameter a
    value: 375.98
    unit: pm
    scope: material
    conditions:
      temperature: not stated on the page
      structure: trigonal, space group R-3m
    method: Value printed on the WebElements crystal structure page
    status: ground
    source: we-crystal
    where: Crystal structures page, a row
  - benchmark: lattice_constant
    label: Lattice parameter c
    value: 1054.75
    unit: pm
    scope: material
    conditions:
      temperature: not stated on the page
      structure: trigonal, space group R-3m
    method: Value printed on the WebElements crystal structure page
    status: ground
    source: we-crystal
    where: Crystal structures page, c row
  - benchmark: molar_volume
    label: Molar volume
    value: 12.95
    unit: cm3
    scope: material
    conditions:
      temperature: not stated on the page
    method: Value printed on the WebElements physics page
    status: ground
    source: we-physics
    where: Physics page, Density properties, Molar volume row
  - benchmark: electronegativity
    label: Pauling electronegativity
    value: 2.18
    unit: Pauling units
    scope: material
    conditions:
      scale: Pauling
    method: Value printed on the WebElements main element page
    status: ground
    source: we-main
    where: Main page, Electronegativity section, Pauling electronegativity row
  - benchmark: mineral_hardness
    label: Mineral hardness
    value: 3.5
    unit: '-'
    scope: material
    conditions:
      scale: mineral hardness scale as printed (no units)
    method: Value printed on the WebElements physics page
    status: ground
    source: we-physics
    where: Physics page, Hardnesses, Mineral hardness row
  - benchmark: brinell_hardness
    label: Brinell hardness
    value: 1440
    unit: MN/m2
    scope: material
    conditions:
      basis: as printed on the page; no load or test conditions given
    method: Value printed on the WebElements physics page
    status: ground
    source: we-physics
    where: Physics page, Hardnesses, Brinell hardness row
corrosion:
  - environment: Dry air at room temperature
    headline: Arsenic is stable in dry air.
    effect: WebElements says arsenic is stable in dry air. No rate or thickness is given.
    rating: none
    conditions:
      basis: rating is the assistant's reading of the wording, not a printed rating
    source: we-chem
    where: Chemistry page, Reaction of arsenic with air paragraph
  - environment: Moist air at room temperature
    headline: The surface tarnishes slowly in moist air.
    effect: WebElements says the surface oxidizes slowly in moist air, first to a bronze tarnish and finally to a black covering. No time, humidity or thickness is given.
    rating: low
    conditions:
      basis: rating is the assistant's reading of the wording; no rate given
    source: we-chem
    where: Chemistry page, Reaction of arsenic with air paragraph
  - environment: Water in the absence of air
    headline: Arsenic does not react with water without air under normal conditions.
    effect: WebElements says arsenic does not react with water in the absence of air under normal conditions.
    rating: none
    conditions:
      basis: normal conditions as stated on the page; no temperature given
    source: we-chem
    where: Chemistry page, Reaction of arsenic with water paragraph
  - environment: Heated in air or oxygen
    headline: Heated arsenic ignites and forms arsenic oxides.
    effect: WebElements says that when heated in air arsenic ignites to form As4O6, with phosphorescence under some conditions. In oxygen it ignites to form As4O10 and As4O6. No ignition temperature is given.
    rating: severe
    conditions:
      basis: rating is the assistant's reading of the ignition wording; no temperature given
    source: we-chem
    where: Chemistry page, Reaction of arsenic with air paragraph and equations
  - environment: Halogens (fluorine, chlorine, bromine and iodine)
    headline: Arsenic reacts with the halogens to form halides.
    effect: WebElements says arsenic reacts with fluorine to form arsenic(V) fluoride, and under controlled conditions with chlorine, bromine and iodine to form the arsenic(III) trihalides.
    rating: severe
    conditions:
      basis: reactions as written on the page; no temperatures or rates given
    source: we-chem
    where: Chemistry page, Reaction of arsenic with the halogens paragraph and equations
risks:
  hazards:
    - text: PubChem's ECHA-based aggregate for arsenic (1439 company reports from 20 notifications) gives H301 toxic if swallowed (above 99.9 percent of reporting companies), H331 toxic if inhaled (above 99.9 percent), H400 very toxic to aquatic life (99.9 percent), H410 very toxic to aquatic life with long lasting effects (above 99.9 percent), and H350 may cause cancer (45.8 percent).
      ghs:
        - 'H301: Toxic if swallowed'
        - 'H331: Toxic if inhaled'
        - 'H350: May cause cancer'
        - 'H400: Very toxic to aquatic life'
        - 'H410: Very toxic to aquatic life with long lasting effects'
        - 'H315: Causes skin irritation'
        - 'H318: Causes serious eye damage'
      source: pubchem-as
      where: Safety and Hazards, GHS Classification, ECHA C&L Notifications Summary (CID 5359596)
    - text: PubChem's summary gives the signal word Danger. The statement text for the precautionary codes was not checked, so use the supplier safety data sheet for the form handled.
      ghs: []
      source: pubchem-as
      where: Safety and Hazards, GHS Classification, Signal Word row
    - text: ATSDR ToxFAQs says that the US Department of Health and Human Services, IARC and EPA all classify inorganic arsenic as a known human carcinogen, and that swallowing it long term causes skin changes and skin cancer. The ToxFAQ covers inorganic arsenic, the form of most concern, rather than the element alone.
      ghs: []
      source: atsdr-faq
      where: ToxFAQs page, health effects answers (carcinogen and skin effects paragraphs)
  failure_risks:
    - mode: Ignition of the element when heated in air
      trigger: Heating in air or oxygen
      consequence: WebElements says arsenic ignites and forms arsenic oxides (As4O6 and As4O10), with phosphorescence under some conditions.
      severity: high
      source: we-chem
      where: Chemistry page, Reaction of arsenic with air paragraph
    - mode: Supply concentrated in few producers
      trigger: Peru, China and Morocco supplied more than 95 percent of world arsenic trioxide in 2025 (USGS)
      consequence: The United States imports all of the arsenic it uses (net import reliance 100 percent in every year from 2021 to 2025e), and China supplied more than 90 percent of US arsenic metal imports through July 2025.
      severity: high
      source: usgs-as-2026
      where: Events, Trends, and Issues; Salient Statistics, Net import reliance row
    - mode: Surface tarnish in moist air
      trigger: Storage in moist air
      consequence: WebElements says the surface oxidizes slowly to a bronze tarnish and finally a black covering. No rate is given.
      severity: low
      source: we-chem
      where: Chemistry page, Reaction of arsenic with air paragraph
  side_effects: []
  handling:
    - text: The US Occupational Safety and Health Administration sets a permissible exposure limit of 10 micrograms per cubic metre of air, as an 8-hour time-weighted average, for airborne inorganic arsenic (ATSDR ToxFAQs).
      source: atsdr-faq
      where: ToxFAQs page, paragraph on the federal government steps to protect people from arsenic
    - text: Breathing high levels of inorganic arsenic causes sore throat and irritated lungs. ATSDR says the level that causes these effects is probably above 100 micrograms per cubic metre for a brief exposure.
      source: atsdr-faq
      where: ToxFAQs page, paragraph on breathing high levels
    - text: Heating arsenic in air ignites it (WebElements), so heating needs a controlled atmosphere.
      source: we-chem
      where: Chemistry page, Reaction of arsenic with air paragraph
  mitigations: []
uses:
  - application: electronics-and-chips
    device: Gallium arsenide and indium gallium arsenide semiconductors
    example: USGS says high-purity (99.9999%) arsenic metal was used to produce GaAs, indium arsenide and InGaAs semiconductors for aerospace devices, satellites, mobile devices, optoelectronic devices and wireless communications.
    source: usgs-as-2026
    where: Events, Trends, and Issues; Domestic Production and Use
  - application: solar-arrays
    device: Gallium arsenide solar cells for space and terrestrial power
    example: USGS says GaAs semiconductors made from high-purity arsenic metal are used in solar cells, space research and telecommunications, and that silicon is the principal competitor with GaAs in solar cells.
    source: usgs-as-2026
    where: Domestic Production and Use; Substitutes
  - application: optics-and-cameras
    device: Specialty infrared optics and shortwave infrared sensors
    example: USGS lists germanium arsenide selenide specialty optical materials and indium gallium arsenide for shortwave infrared technology among the uses of high-purity arsenic metal.
    source: usgs-as-2026
    where: Domestic Production and Use
  - application: electronics-and-chips
    device: Dopant in solid-state devices such as transistors
    example: WebElements lists doping agent in solid-state devices such as transistors among the uses of arsenic. The page says its uses are gathered from several sources and from anecdotal comments.
    source: we-uses
    where: Uses page, list of uses
supply:
  - subject: Arsenic (arsenic trioxide, the main commercial compound, and high-purity metal)
    abundance: No crustal abundance figure was read in this pass. USGS says arsenic is recovered from copper, gold and lead smelter flue dust and from roasting arsenopyrite, and that world reserves were not reported but were estimated to be more than 20 times world production.
    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
    us_position: 'US imports in 2025e were 6300 t of arsenic in total (740 t metal and 5500 t compounds), and net import reliance was 100 percent in every year from 2021 to 2025e. Import sources from 2021 to 2024: China supplied 95 percent of arsenic metal imports and 45 percent of all arsenic imports. China also supplied more than 80 percent of US arsenic trioxide imports through July 2025. The metal price was 1.85 dollars per pound in 2025e.'
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (IEA summary of the final list names arsenic)
        listed: true
      - list: EU critical raw materials list (2023 fifth list of 34 CRMs, Regulation (EU) 2024/1252)
        listed: true
    recycling: 'USGS: arsenic metal was contained in new scrap recycled during GaAs semiconductor manufacturing. No arsenic was known to be recovered from scrap electronic boards during recycling for other metals.'
    substitutes:
      - 'USGS: silicon is the principal competitor with GaAs in solar cells, and no effective substitutes exist for GaAs in many defense-related applications. Indium phosphide can replace GaAs in some infrared laser diodes.'
    source: usgs-as-2026
    where: World Production and Capacity table (2025, arsenic trioxide gross weight; shares calculated by Space Mushroom against the 61000 t world total); Import Sources (2021 to 2024); Salient Statistics; Recycling; Substitutes
media: []
documents:
  - title: USGS Mineral Commodity Summaries 2026, Arsenic
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-arsenic.pdf
    year: 2026
  - title: 'PubChem: Arsenic (CID 5359596), GHS classification summary'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/5359596
    year: 2026
  - title: 'ATSDR ToxFAQs: Arsenic'
    type: report
    url: https://wwwn.cdc.gov/TSP/ToxFAQs/ToxFAQsDetails.aspx?faqid=18&toxid=3
gaps:
  - 'Electrical resistivity: WebElements prints it as 33 with a 10 to the minus 8 exponent in ohm metres. It is left out because the value is written in exponent form.'
  - Dopant data (solubility of arsenic in silicon or germanium, carrier concentration, donor behaviour) were not found in a source read in this pass.
  - 'Crustal abundance: the WebElements abundance field was not captured, and USGS gives no abundance figure.'
  - 'Occupational exposure limit from NIOSH: the NIOSH pocket guide page returned Access Denied. The OSHA limit is taken from the ATSDR ToxFAQ instead, and it is for inorganic arsenic.'
  - 'Acid and alkali corrosion: WebElements has reaction sections for acids and bases, but their text was not captured.'
  - No vacuum, radiation, thermal-vacuum or flight result for the element was found. Its space use is through GaAs devices and solar cells, as USGS describes.
  - Hazard data for the elemental form rest on the PubChem aggregate and the ATSDR ToxFAQ (which covers inorganic arsenic). No supplier safety data sheet for the element was read.
  - Melting point is printed under pressure, and WebElements gives no ambient-pressure melting point.
  - 'Property names not in spores/property-canon.yaml and used here: enthalpy_of_fusion, enthalpy_of_sublimation, enthalpy_of_atomisation, molar_volume, electronegativity, mineral_hardness, brinell_hardness, lattice_constant. Density, elastic_modulus, bulk_modulus, thermal_conductivity, melting_point, boiling_point and electronegativity are canonical or aliased.'
  - The EU list and the USGS 2025 list are cited through the EC page and the IEA summary of the USGS list. The USGS critical-minerals page itself could not be opened.
sources:
  we-physics:
    title: 'WebElements, Arsenic: physical properties (density, elastic, hardness and electrical data)'
    url: https://www.webelements.com/arsenic/physics.html
    kind: web
    license: page content, cited as published
  we-thermochemistry:
    title: 'WebElements, Arsenic: thermochemistry (melting and boiling points, enthalpies)'
    url: https://www.webelements.com/arsenic/thermochemistry.html
    kind: web
    license: page content, cited as published
  we-crystal:
    title: 'WebElements, Arsenic: crystal structures (space group and lattice parameters)'
    url: https://www.webelements.com/arsenic/crystal_structure.html
    kind: web
    license: page content, cited as published
  we-main:
    title: 'WebElements, Arsenic: element page (relative atomic mass, electronegativity)'
    url: https://www.webelements.com/arsenic/
    kind: web
    license: page content, cited as published
  we-chem:
    title: 'WebElements, Arsenic: chemistry (reactions with air, water and halogens)'
    url: https://www.webelements.com/arsenic/chemistry.html
    kind: web
    license: page content, cited as published
  we-uses:
    title: 'WebElements, Arsenic: uses'
    url: https://www.webelements.com/arsenic/uses.html
    kind: web
    license: page content, cited as published
  pubchem-as:
    title: PubChem compound record, Arsenic (CID 5359596), GHS classification
    id: CID 5359596
    url: https://pubchem.ncbi.nlm.nih.gov/compound/5359596
    kind: database
    year: 2026
    license: public domain (NCBI)
  nist-as:
    title: NIST, Atomic weights and isotopic compositions for arsenic (As)
    url: https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=As&all=all&ascii=html
    kind: database
    license: public domain (NIST)
  usgs-as-2026:
    title: USGS Mineral Commodity Summaries 2026, Arsenic (February 2026)
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-arsenic.pdf
    kind: report
    year: 2026
    license: public domain (USGS)
  atsdr-faq:
    title: ATSDR ToxFAQs, Arsenic
    url: https://wwwn.cdc.gov/TSP/ToxFAQs/ToxFAQsDetails.aspx?faqid=18&toxid=3
    kind: handbook
    license: public domain (CDC/ATSDR)
  iea-crit-2025:
    title: IEA, Final List of Critical Minerals 2025 (summary of the USGS list, updated July 2026)
    url: https://www.iea.org/policies/31799
    kind: web
    year: 2026
    license: page content, cited as published
  ec-crm:
    title: European Commission, Critical raw materials (2023 fifth list of 34 CRMs, Regulation (EU) 2024/1252)
    url: https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en
    kind: web
    year: 2024
    license: European Commission web page
license: CC-BY-4.0
checked_values: 15
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 15
  unreachable: 1
  caveats: 2
  note: Written by an AI assistant from pages fetched on 2026-10-26. The NIOSH page was blocked, and the USGS critical-minerals page could not be opened.
story:
  recipe:
    line: Arsenic is the element As (PubChem). WebElements gives its crystal as trigonal, space group R-3m. USGS says arsenic is obtained from copper, gold and lead smelter flue dust and by roasting arsenopyrite, and that high-purity metal is made for GaAs semiconductors.
    parts:
      - name: Arsenic
        symbol: As
        atoms: 1
        atomic_weight: 74.921595
        share_percent: 100
        role: The element itself. High-purity metal is the feedstock for GaAs and InGaAs semiconductors (USGS).
        source: nist-as
        where: Atomic weights table, As row (standard atomic weight with uncertainty printed in the table)
  risk_groups:
    - title: For people
      level: 3
      verdict: Toxic if swallowed or inhaled; known human carcinogen
      lead: PubChem's aggregate classes arsenic as toxic if swallowed or inhaled, and the US health department, IARC and EPA classify inorganic arsenic as a human carcinogen.
      points:
        - label: Swallowing or breathing
          line: PubChem's aggregate gives H301 (toxic if swallowed) and H331 (toxic if inhaled) for more than 99.9 percent of the companies that report those codes. ATSDR says high levels of inorganic arsenic in air cause sore throat and irritated lungs.
        - label: Long-term exposure
          line: ATSDR says that long-term oral exposure to inorganic arsenic causes darkened patches of skin and wart-like corns, and that it can increase the risk of cancer in the liver, bladder and lungs.
        - label: Workplace limit
          line: The OSHA permissible exposure limit for airborne inorganic arsenic is 10 micrograms per cubic metre, as an 8-hour average, according to ATSDR.
    - title: If it fails
      lead: The failure routes in the sources read are ignition on heating and a supply that depends on a few producers.
      points:
        - label: Heat
          line: WebElements says heated arsenic ignites in air and forms arsenic oxides, with phosphorescence under some conditions.
        - label: Supply
          line: USGS says Peru, China and Morocco supplied more than 95 percent of world arsenic trioxide in 2025, and the United States imports all of the arsenic it uses.
  why: 'Arsenic is a metalloid. Its main technical use is in semiconductors: high-purity arsenic metal makes gallium arsenide and related compounds used in satellites, solar cells and wireless devices. Its toxicity is high, so PubChem and ATSDR both flag it, and handling needs care.'
  uses:
    - where: Semiconductors and solar cells
      line: USGS says high-purity arsenic metal makes GaAs, indium arsenide and InGaAs semiconductors used in satellites, aerospace devices, photovoltaic applications and mobile devices.
    - where: Infrared and specialty optics
      line: USGS lists germanium arsenide selenide specialty optical materials and indium gallium arsenide for shortwave infrared sensing as uses of the metal.
    - where: Dopant
      line: WebElements lists a doping agent in solid-state devices such as transistors among the uses of arsenic.
  can_do:
    - label: Density
      value: 5727 kg/m3
      benchmark: density
      line: The solid has a density of 5727 kg/m3 (WebElements), printed as 5727 kg m-3.
    - label: Melt
      value: 817 °C under pressure
      benchmark: melting_point
      line: WebElements gives 817 °C as the melting point under pressure. It says there is no liquid phase at normal pressure, and that the element sublimes at 614 °C.
    - label: Carry heat
      value: 50 W m-1 K-1
      benchmark: thermal_conductivity
      line: Thermal conductivity is printed as 50 W m-1 K-1 (WebElements), with no temperature given.
    - label: Stiffness
      value: 8 GPa
      benchmark: elastic_modulus
      line: WebElements prints Young's modulus as 8 GPa and the bulk modulus as 22 GPa.
  compare: The table compares the element's density, melting point and thermal conductivity. Arsenic is best known in devices through its compounds with gallium and indium, which carry most of the semiconductor and optical uses cited by the USGS. The element itself is toxic and ignites when heated in air.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Melting point under pressure
      benchmark: melting_point
    - label: Thermal conductivity
      benchmark: thermal_conductivity
  handling:
    - 'Treat arsenic as toxic: PubChem reports H301 and H331 (toxic if swallowed or inhaled) for most reporting companies.'
    - Keep airborne exposure under the OSHA limit of 10 micrograms per cubic metre, an 8-hour average, for inorganic arsenic (ATSDR).
    - Heating in air ignites the element (WebElements), so heat it under a controlled atmosphere.
  good_for:
    - Source of high-purity arsenic metal for GaAs and InGaAs semiconductors used in satellites and solar cells (USGS).
    - Dopant in solid-state devices such as transistors (WebElements).
  watch_out:
    - 'Toxicity: PubChem reports H301 and H331 for most reporting companies, and ATSDR classes inorganic arsenic as a known human carcinogen.'
    - Heating in air ignites the element, forming arsenic oxides (WebElements).
    - 'Supply concentration: USGS says Peru, China and Morocco supplied more than 95 percent of world arsenic trioxide in 2025.'
  verdict: Arsenic is well documented as a semiconductor feedstock. Its density, melting point and thermal constants come from WebElements, and its use and supply come from the USGS. Its toxicity is the limiting factor. The sources read did not give a dopant solubility figure, a crustal abundance or an NIOSH exposure limit.