Boric acid (H3BO3)

spore: profile
id: boric-acid
spore_version: 0.2
family: boron-compounds
name: Boric acid (H3BO3)
role: neutron poison and soluble boron source
category: shielding
type: water-and-ice
summary: |
  Boric acid (H3BO3, also written B(OH)3) is a boron compound that dissolves in water. Wikipedia says it is used in some nuclear power plants as a neutron poison. PubChem gives its density as 1.435 g/cm3 at 25 °C and its first pKa as 9.24, and its GHS record classes it as a reproductive toxicant (H360FD).
best_for: 'Soluble boron for neutron absorption in water (Wikipedia: used in some nuclear power plants as a neutron poison)'
weakest_at: 'Handling: classed as a reproductive toxicant (H360FD) by PubChem, and the dust irritates the eyes, skin and airways'
identity:
  formula: H3BO3 (orthoboric acid, written B(OH)3)
  cas: 10043-35-3
  source: nist-webbook
  where: NIST WebBook, Formula and CAS Registry Number 10043-35-3 (its molecular weight prints with no unit and is not used)
tags:
  environments: []
  stresses: []
  applications: []
properties:
  - benchmark: density
    label: Density, boric acid
    value: 1.435
    unit: g/cm3
    scope: material
    conditions:
      temperature: 25 °C, as printed on the PubChem entry (1.435 @25 °C)
    method: Experimental value printed in the PubChem record; no test standard named
    status: ground
    source: pubchem-boric-acid
    where: Chemical and Physical Properties, Experimental Properties, Density
  - benchmark: melting_point
    label: Melting point, boric acid (Wikipedia infobox)
    value: 170.9
    unit: °C
    scope: material
    conditions:
      basis: printed as 170.9 °C (339.6 °F; 444.0 K); ICSC instead gives decomposition at 171 °C
    method: Value printed in the Wikipedia infobox; no test standard named
    status: ground
    note: 'Two sources differ on the thermal behaviour: this melting point (Wikipedia) and the decomposition temperature from ICSC are both recorded.'
    source: wikipedia-boric-acid
    where: Infobox, Properties, Melting point row
  - benchmark: decomposition_temperature
    label: Decomposition temperature, ICSC card
    value: 171
    unit: °C
    scope: material
    conditions:
      basis: printed as 'Decomposes at 171°C' where a melting point would normally appear
    method: Value printed on the ICSC card; no test standard named
    status: ground
    source: icsc-0991
    where: Physical and Chemical Information, melting point line
  - benchmark: decomposition_temperature
    label: Decomposition onset, PubChem chemical dangers text
    value: 100
    bound: lower
    unit: °C
    scope: material
    conditions:
      basis: printed as 'Decomposes above 100 °C' in the PubChem chemical dangers text
    method: Summary statement in the PubChem record; no test method printed
    status: ground
    note: The same PubChem record also prints 'Stable up to 100 °C' in its stability line, which conflicts with the 171 °C figure from ICSC.
    source: pubchem-boric-acid
    where: Safety and Hazards, Safety and Hazard Properties, Chemical Dangers
  - benchmark: molar_mass
    label: Molar mass, boric acid
    value: 61.83
    unit: g·mol−1
    scope: material
    conditions:
      basis: printed in the Wikipedia infobox as 61.83 g·mol−1
    method: Infobox value; no measurement method printed
    status: calculated
    source: wikipedia-boric-acid
    where: Infobox, Properties, Molar mass row
  - benchmark: pka
    label: Acid dissociation constant, first proton (pKa)
    value: 9.24
    unit: '-'
    scope: material
    conditions:
      basis: first proton (Wikipedia gives 9.24 for the first proton); PubChem prints pKa = 9.24
      temperature: 25 °C, as printed for the dissociation constant
    method: Value printed in the PubChem dissociation constants entry; Wikipedia also prints 9.24
    status: ground
    source: pubchem-boric-acid
    where: Chemical and Physical Properties, Experimental Properties, Dissociation Constants
  - benchmark: water_solubility
    label: Solubility in water at 20 °C (Wikipedia)
    value: 4.72
    unit: g/100 mL
    scope: material
    conditions:
      temperature: 20 °C
      solvent: water
    method: Value printed in the Wikipedia infobox; no method named
    status: ground
    note: ICSC gives 5.6 g/100ml at 20 °C, a different value; both are recorded and neither is averaged.
    source: wikipedia-boric-acid
    where: Infobox, Properties, Solubility in water row, 20 °C entry
  - benchmark: water_solubility
    label: Solubility in water at 20 °C (ICSC)
    value: 5.6
    unit: g/100ml
    scope: material
    conditions:
      temperature: 20 °C
      solvent: water
    method: Value printed on the ICSC card; no method named
    status: ground
    note: Disagrees with the 4.72 g/100 mL at 20 °C printed by Wikipedia; both are recorded.
    source: icsc-0991
    where: Physical and Chemical Information, Solubility in water, g/100ml at 20°C line
  - benchmark: water_solubility
    label: Solubility in water at 100 °C (Wikipedia)
    value: 27.53
    unit: g/100 mL
    scope: material
    conditions:
      temperature: 100 °C
      solvent: water
    method: Value printed in the Wikipedia infobox; no method named
    status: ground
    source: wikipedia-boric-acid
    where: Infobox, Properties, Solubility in water row, 100 °C entry
  - benchmark: tlv_twa
    label: TLV, time-weighted average, inhalable fraction
    value: 2
    unit: mg/m3
    scope: material
    conditions:
      basis: inhalable fraction, as TWA, as printed on the ICSC card
    method: Occupational limit printed on the ICSC card
    status: ground
    source: icsc-0991
    where: Exposure Control and Personal Protection, TLV row
  - benchmark: tlv_stel
    label: TLV, short-term exposure limit, inhalable fraction
    value: 6
    unit: mg/m3
    scope: material
    conditions:
      basis: inhalable fraction, as STEL, as printed on the ICSC card
    method: Occupational limit printed on the ICSC card
    status: ground
    source: icsc-0991
    where: Exposure Control and Personal Protection, TLV row (6 mg/m3 as STEL)
  - benchmark: mak_limit
    label: MAK, inhalable fraction (German limit, as printed)
    value: 10
    unit: mg/m3
    scope: material
    conditions:
      basis: inhalable fraction, as printed on the ICSC card
    method: Occupational limit printed on the ICSC card
    status: ground
    source: icsc-0991
    where: Exposure Control and Personal Protection, MAK row
  - benchmark: boron10_abundance
    label: Boron-10 share of natural boron (element-level figure)
    value: 19.9
    unit: '%'
    scope: material
    conditions:
      basis: 'natural boron, as printed: boron has two naturally occurring and stable isotopes, 11B (80.1%) and 10B (19.9%)'
    method: Element-level figure printed in the Wikipedia Boron article; boric acid carries boron with this isotope mix, and no isotope measurement on boric acid itself was read
    status: ground
    source: wikipedia-boron
    where: Characteristics of the element, Isotopes
  - benchmark: boron11_abundance
    label: Boron-11 share of natural boron (element-level figure)
    value: 80.1
    unit: '%'
    scope: material
    conditions:
      basis: natural boron, as printed in the same sentence as 10B (19.9%)
    method: Element-level figure printed in the Wikipedia Boron article
    status: ground
    source: wikipedia-boron
    where: Characteristics of the element, Isotopes
corrosion:
  - environment: Metal surfaces in contact with boric acid solution
    headline: PubChem says boric acid attacks metals and that this produces hydrogen.
    effect: The PubChem chemical dangers summary says that the solution in water is a weak acid, that boric acid attacks metals, and that this produces hydrogen and a fire and explosion hazard. It prints no corrosion rate, metal, concentration or test condition.
    rating: unknown
    conditions:
      basis: qualitative summary in the PubChem record; no test method or corrosion rate printed
    source: pubchem-boric-acid
    where: Safety and Hazards, Safety and Hazard Properties, Chemical Dangers
risks:
  hazards:
    - text: 'Reproductive toxicity: the PubChem GHS summary gives hazard statement H360FD, ''May damage fertility; May damage the unborn child'', with signal word Danger and Reproductive toxicity category 1B. ICSC prints ''May damage fertility or the unborn child'' in its Classification and Labelling section.'
      ghs:
        - H360FD
      source: pubchem-boric-acid
      where: Safety and Hazards, Hazards Identification, GHS Classification (signal word, hazard statements); ICSC Classification and Labelling
    - text: 'Skin and eyes: PubChem prints ''Boric acid irritates the eyes, skin, and the respiratory tract.'' ICSC lists redness and pain for the eyes, and says repeated or prolonged skin contact may cause dermatitis.'
      ghs: []
      source: pubchem-boric-acid
      where: Safety and Hazards, Skin, Eye, and Respiratory Irritations; ICSC Exposure and Health Effects
    - text: 'Ingestion and inhalation: ICSC lists nausea, vomiting, diarrhoea, abdominal pain and skin rash after ingestion, and cough and sore throat after inhalation of dust. It says the substance can be absorbed into the body by inhalation of dust and by ingestion.'
      ghs: []
      source: icsc-0991
      where: Exposure and Health Effects, Inhalation and Ingestion rows
  failure_risks:
    - mode: Heating the powder or solution to decomposition
      trigger: 'Heating above the decomposition temperature (PubChem: above 100 °C; ICSC: 171 °C)'
      consequence: PubChem says decomposition produces water and irritant boric anhydride. The chemical dangers text also says the solution in water is a weak acid.
      severity: low
      source: pubchem-boric-acid
      where: Safety and Hazards, Safety and Hazard Properties, Chemical Dangers
    - mode: Dust drawn into the airways or eyes during handling
      trigger: Handling dry powder without dust control
      consequence: ICSC lists cough and sore throat as inhalation symptoms and redness and pain as eye symptoms. It notes the substance can be absorbed into the body by inhalation of dust.
      severity: moderate
      source: icsc-0991
      where: Exposure and Health Effects, Inhalation and Eyes rows
  side_effects: []
  handling:
    - text: 'Spill clean-up: PubChem advises dampening the solid spill with water, then transferring the dampened material to a suitable container.'
      source: pubchem-boric-acid
      where: Safety and Hazards, Handling and Storage, Nonfire Spill Response
    - text: 'Respiratory protection: PubChem advises a particulate filter respirator adapted to the airborne concentration of the substance.'
      source: pubchem-boric-acid
      where: Safety and Hazards, Accidental Release Measures, Spillage Disposal
    - text: 'Storage: PubChem advises storing in well-closed containers, separated from strong bases.'
      source: pubchem-boric-acid
      where: Safety and Hazards, Handling and Storage, Storage Conditions and Safe Storage
    - text: 'Airborne limits printed by ICSC for dust: TLV 2 mg/m3 as TWA, 6 mg/m3 as STEL (inhalable fraction), and MAK 10 mg/m3.'
      source: icsc-0991
      where: Exposure Control and Personal Protection, TLV and MAK rows
  mitigations: []
uses:
  - application: radiation-shielding
    device: Neutron poison in some nuclear power plants
    example: 'Wikipedia: boric acid is used in some nuclear power plants as a neutron poison, and the boron in it reduces the probability of thermal fission by absorbing some thermal neutrons.'
    source: wikipedia-boric-acid
    where: Nuclear power section
  - application: electronics-and-chips
    device: Semiconductor production (boron chemicals)
    example: USGS says boron minerals and chemicals were used as a component in abrasives, cleaning products, insecticides, insulation, and in the production of semiconductors in the United States. The source treats this as boron in general, not boric acid alone.
    source: usgs-mcs2026-boron
    where: Domestic Production and Use paragraph
supply:
  - subject: Boron (borates and boric acid)
    producers:
      - country: Turkey
        year: 2025
      - country: China
        year: 2025
      - country: Chile
        year: 2025
      - country: Bolivia
        year: 2025
      - country: Peru
        year: 2025
      - country: Russia
        year: 2025
      - country: Argentina
        year: 2025
      - country: Germany
        year: 2025
    critical_lists:
      - list: USGS 2025 List of Critical Minerals (boron added in the final list, per usgs-mcs2026-boron and usgs-crit2025)
        listed: true
      - list: EU critical raw materials list, Boron/Borate (per ec-crm)
        listed: true
    recycling: 'USGS: recycling of boron is listed as ''Insignificant.'''
    substitutes:
      - 'USGS: substitution of other materials for boron is possible in detergents, enamels, insulation, and soaps; sodium percarbonate can replace borates in detergents.'
    where: World Production and Reserves table, 2025 column (production printed without units; the world total is marked XX, which USGS says cannot be calculated; the United States is marked W, withheld); Recycling; Substitutes. Lists from usgs-mcs2026-boron, usgs-crit2025 and ec-crm.
    source: usgs-mcs2026-boron
documents:
  - title: 'ICSC 0991: Boric acid (International Chemical Safety Card)'
    type: database
    url: https://chemicalsafety.ilo.org/dyn/icsc/showcard.display?p_card_id=0991
  - title: 'PubChem compound record: Boric acid (CID 7628), GHS and property sections'
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/compound/Boric-acid
  - title: 'Mineral Commodity Summaries 2026: Boron (USGS)'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-boron.pdf
    year: 2026
  - title: 'NIST Chemistry WebBook: Boric acid (identifiers)'
    type: database
    url: https://webbook.nist.gov/cgi/cbook.cgi?ID=C10043353&Units=SI
gaps:
  - No neutron-capture cross section for boric acid or for boron-10 was read in a fetched source, so the neutron-absorption role has no number of its own in this record.
  - 'Corrosion of carbon or low-alloy steel by boric acid in reactor coolant has no source here: the NRC Bulletin 2002-01 PDF and HTML addresses both returned HTTP 404 and the NRC glossary returned HTTP 403.'
  - The CDC ATSDR Toxicological Profile for Boron could not be read (the server rejected the download), so no animal toxicity dose or reproductive-effect level is recorded.
  - The EPA boric acid page returned not found, and the web search budget ran out, so no manufacturer safety data sheet for boric acid was read. The hazard data rest on ICSC and PubChem.
  - 'Vapour pressure: ICSC gives ''negligible'' and PubChem prints it in scientific notation, so no vapour-pressure value is recorded.'
  - 'Melting point is not settled by one source: Wikipedia gives a melting point and ICSC gives decomposition. Both are recorded side by side and the question is left open.'
  - Solubility at 20 °C differs between Wikipedia and ICSC; both values are recorded and neither is averaged.
  - 'Decomposition onset differs: PubChem says it decomposes above 100 °C and is stable up to 100 °C, while ICSC gives 171 °C. Both are recorded.'
  - USGS producer tonnages are printed without units and the world total is marked XX, so producer shares are not calculated and only the countries are listed.
  - No space flight, vacuum or radiation-test data for boric acid were found; the uses listed are terrestrial, so no space environment tags are set.
  - The boron-10 and boron-11 shares are element-level figures from Wikipedia's Boron article, not isotope measurements on boric acid.
  - No designations other than the CAS number (10043-35-3) were printed in the sources read, so no UNS, EN or trade names are listed.
sources:
  wikipedia-boric-acid:
    title: Boric acid (Wikipedia)
    id: en.wikipedia.org/wiki/Boric_acid
    url: https://en.wikipedia.org/wiki/Boric_acid
    kind: web
    license: CC BY-SA 4.0 (Wikipedia text, cited not reproduced)
  icsc-0991:
    title: 'International Chemical Safety Card 0991: Boric acid'
    id: ICSC 0991
    url: https://chemicalsafety.ilo.org/dyn/icsc/showcard.display?p_card_id=0991
    kind: database
    license: ICSC card, cited not reproduced
  pubchem-boric-acid:
    title: PubChem compound record, Boric acid (CID 7628), full property and safety data
    id: CID 7628; CAS 10043-35-3
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/7628/JSON
    kind: database
    license: public domain (NCBI)
  nist-webbook:
    title: NIST Chemistry WebBook, Boric acid (identifiers)
    id: NIST WebBook, CAS 10043-35-3
    url: https://webbook.nist.gov/cgi/cbook.cgi?ID=C10043353&Units=SI
    kind: database
    license: public domain (NIST)
  usgs-mcs2026-boron:
    title: Mineral Commodity Summaries 2026, Boron
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-boron.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-crit2025:
    title: About the 2025 List of Critical Minerals (USGS)
    id: Final 2025 List of Critical Minerals
    url: https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals
    year: 2025
    kind: web
    license: public domain (USGS)
  ec-crm:
    title: Critical raw materials (European Commission, list including Boron/Borate)
    id: Regulation (EU) 2024/1252
    url: https://single-market-economy.ec.europa.eu/sectors/raw-materials/areas-specific-interest/critical-raw-materials_en
    year: 2024
    kind: web
    license: European Commission web page
  wikipedia-boron:
    title: Boron (Wikipedia)
    id: en.wikipedia.org/wiki/Boron
    url: https://en.wikipedia.org/wiki/Boron
    kind: web
    license: CC BY-SA 4.0 (Wikipedia text, cited not reproduced)
  wikipedia-hydrogen:
    title: Hydrogen (Wikipedia)
    id: en.wikipedia.org/wiki/Hydrogen
    url: https://en.wikipedia.org/wiki/Hydrogen
    kind: web
    license: CC BY-SA 4.0 (Wikipedia text, cited not reproduced)
  wikipedia-oxygen:
    title: Oxygen (Wikipedia)
    id: en.wikipedia.org/wiki/Oxygen
    url: https://en.wikipedia.org/wiki/Oxygen
    kind: web
    license: CC BY-SA 4.0 (Wikipedia text, cited not reproduced)
license: CC-BY-4.0
updated: '2026-11-02'
review:
  status: draft
  method: assistant
  checked_values: 14
  unreachable: 0
  caveats: 3
  note: Values read by an AI assistant on 2026-11-02 from fetched pages; 3 values carry a source conflict (melting or decomposition, solubility at 20 °C, decomposition onset) and both sides are recorded.
story:
  recipe:
    line: 'Boric acid is H3BO3, also written B(OH)3 in Wikipedia''s lead: one boron atom bonded to three hydroxyl groups. Wikipedia''s history section says orthoboric acid was first prepared from borax by the action of mineral acids.'
    parts:
      - name: Boron
        symbol: B
        atoms: 1
        atomic_weight: 10.81
        source: wikipedia-boron
        where: Infobox, Standard atomic weight row, abridged value (printed without unit)
        role: The central atom. Boron is the element that absorbs neutrons in the boron-10 isotope, which is 19.9% of natural boron.
      - name: Hydrogen
        symbol: H
        atoms: 3
        atomic_weight: 1.008
        source: wikipedia-hydrogen
        where: Infobox, Standard atomic weight row, abridged value (printed without unit)
        role: Three hydrogens sit on the hydroxyl groups, which give the acid its weak acidity (pKa 9.24).
      - name: Oxygen
        symbol: O
        atoms: 3
        atomic_weight: 15.999
        source: wikipedia-oxygen
        where: Infobox, Standard atomic weight row, abridged value (printed without unit)
        role: Three oxygens form the hydroxyl groups, which bind the hydrogen to the boron.
  risk_groups:
    - title: For people
      level: 3
      verdict: Reproductive toxicant (H360FD)
      lead: ICSC and PubChem both classify boric acid as a reproductive toxicant. The powder also irritates the eyes, skin and airways.
      points:
        - label: Fertility and the unborn child
          line: PubChem's GHS summary gives H360FD, 'May damage fertility; May damage the unborn child', with signal word Danger. ICSC prints 'May damage fertility or the unborn child'.
        - label: Dust
          line: ICSC lists cough and sore throat as inhalation symptoms and says the substance can be absorbed by inhaling dust. The TLV is 2 mg/m3 as TWA, and the STEL is 6 mg/m3.
        - label: Ingestion
          line: ICSC lists nausea, vomiting, diarrhoea, abdominal pain and skin rash after ingestion.
    - title: If the powder is heated
      level: 2
      verdict: Decomposes above 100 °C per PubChem
      lead: Heated, boric acid gives off water and boric anhydride. ICSC gives 171 °C as the decomposition temperature, and PubChem says it decomposes above 100 °C.
      points:
        - label: Decomposition
          line: PubChem says it decomposes above 100 °C and produces water and irritant boric anhydride. ICSC gives 171 °C.
    - title: Handling and spills
      level: 1
      verdict: Dampen spills and keep dust down
      lead: The safety data sheets and PubChem advise limiting dust and cleaning spills wet.
      points:
        - label: Spills
          line: PubChem advises dampening the spilled solid with water before sweeping it into a container, with a particulate filter respirator.
        - label: Storage
          line: PubChem advises well-closed containers, separated from strong bases.
  why: Boric acid (H3BO3, also written B(OH)3) is a boron compound that dissolves in water. Wikipedia says it is used in some nuclear power plants as a neutron poison, because the boron in it absorbs some thermal neutrons. Boron-10 makes up 19.9% of natural boron. This record covers the acid itself, which ICSC and PubChem both treat as a reproductive hazard.
  uses:
    - where: Nuclear power plants
      line: Wikipedia says boric acid is used in some nuclear power plants as a neutron poison. The boron in it reduces the probability of thermal fission by absorbing some thermal neutrons.
    - where: Semiconductors and other uses
      line: The USGS Mineral Commodity Summaries say boron minerals and chemicals were used in abrasives, cleaning products, insecticides, insulation and the production of semiconductors in the United States. That statement covers boron in general.
  can_do:
    - label: Neutron absorption
      line: The boron in boric acid absorbs some thermal neutrons, which reduces the chance of fission in the nuclear plants that use it (Wikipedia). The boron-10 share of natural boron is 19.9%.
      benchmark: boron10_abundance
    - label: Density
      benchmark: density
      value: 1.435 g/cm3
      line: Density is 1.435 g/cm3 at 25 °C, per the PubChem record.
    - label: Melting point
      benchmark: melting_point
      value: 170.9 °C
      line: Wikipedia prints a melting point of 170.9 °C, while ICSC lists decomposition at 171 °C instead.
    - label: Solubility
      benchmark: water_solubility
      value: 4.72 g/100 mL at 20 °C
      line: At 20 °C, 4.72 g/100 mL dissolves per Wikipedia, and ICSC gives 5.6 g/100ml. The Wikipedia figure rises to 27.53 g/100 mL at 100 °C.
    - label: Acidity
      benchmark: pka
      value: pKa 9.24
      line: The first pKa is 9.24, so the solution is a weak acid (PubChem).
    - label: Exposure limit
      benchmark: tlv_twa
      value: 2 mg/m3 TWA
      line: ICSC gives a TLV of 2 mg/m3 as TWA for inhalable dust, with a 6 mg/m3 STEL and a MAK of 10 mg/m3.
  compare: Boric acid dissolves in water, which is the main difference from a solid boron shield. At 20 °C it dissolves to 4.72 g/100 mL per Wikipedia or 5.6 g/100ml per ICSC, and it rises to 27.53 g/100 mL at 100 °C. Its density is 1.435 g/cm3 at 25 °C (PubChem). Its melting point is 170.9 °C per Wikipedia, while ICSC gives decomposition at 171 °C instead. The table compares density, melting point and solubility.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Melting point
      benchmark: melting_point
    - label: Water solubility at 20 °C
      benchmark: water_solubility
  handling:
    - Dampen spilled powder with water before sweeping it up, and use a particulate filter respirator for the cleanup.
    - Keep it in well-closed containers, away from strong bases.
    - Keep dust under the 2 mg/m3 TWA limit (ICSC), and avoid breathing it.
  good_for:
    - Soluble boron for neutron absorption in water, where Wikipedia says it is used in some nuclear power plants.
    - Known solubility data at several temperatures, from 20 °C to 100 °C, for mixing and dosing calculations.
  watch_out:
    - PubChem classes boric acid as a reproductive toxicant (H360FD, signal word Danger).
    - The dust irritates the eyes, skin and airways, per PubChem and ICSC.
    - 'The sources disagree on heat behaviour: 170.9 °C melting point (Wikipedia), 171 °C decomposition (ICSC), and decomposition above 100 °C (PubChem).'
    - 'The sources disagree on solubility at 20 °C: 4.72 g/100 mL (Wikipedia) against 5.6 g/100ml (ICSC).'
  verdict: Boric acid is a soluble neutron absorber used in some nuclear power plants, but ICSC and PubChem treat it as a reproductive hazard, so it should be handled as a toxic dust.