{
  "spore": "profile",
  "id": "barium",
  "spore_version": "0.2",
  "family": "alkali-and-alkaline-earth-metals",
  "name": "Barium metal",
  "abbreviation": "Ba",
  "role": "getter",
  "category": "metals",
  "type": "heavy-metals",
  "summary": "Barium is a soft, silvery alkaline earth metal. It reacts with water, giving off hydrogen, and it oxidizes readily in moist air. Its spaceflight role comes from barium oxide, which is pressed into the tungsten emitters of dispenser cathodes that supply the electrons used by ion and Hall thrusters and by plasma contactors. Barium alloys with aluminium or magnesium also serve as getters that remove residual gases in electronic vacuum tubes.\n",
  "best_for": "Getter alloys and barium-impregnated electron emitters inside a sealed vacuum, where the metal is never exposed to water or air",
  "weakest_at": "Any contact with water or moist air: it reacts at once and releases hydrogen, and powdered barium reacts violently with air",
  "identity": {
    "formula": "Ba",
    "cas": "7440-39-3",
    "crystal_system": "cubic",
    "designations": [],
    "source": "atsdr-2007",
    "where": "Table 4-2, Barium column: CAS registry and Physical description (silvery-yellow metal; cubic)"
  },
  "tags": {
    "environments": [
      "low-earth-orbit"
    ],
    "stresses": [
      "vacuum-and-outgassing"
    ],
    "applications": [
      "electronics-and-chips",
      "propulsion-and-tanks",
      "structures"
    ]
  },
  "properties": [
    {
      "benchmark": "density",
      "value": 3.51,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "temperature": "20 C"
      },
      "method": "Value printed in the supplier safety data sheet",
      "status": "ground",
      "source": "aci-ba-sds",
      "where": "Section 9, Physical and chemical properties: Density at 20 C",
      "source_detail": {
        "title": "Barium safety data sheet, ACI Alloys (Material Name: Barium)",
        "url": "https://www.acialloys.com/wp-content/uploads/msds/ba.html",
        "kind": "datasheet",
        "license": "supplier document"
      }
    },
    {
      "benchmark": "density",
      "value": 3.62,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "temperature": "not stated by source"
      },
      "method": "Value printed in the ATSDR profile",
      "status": "ground",
      "note": "The supplier sheet gives 3.51 g/cm3 at 20 C. The profile keeps both values and does not average them.",
      "source": "atsdr-2007",
      "where": "Table 4-2, Barium column: Density",
      "source_detail": {
        "title": "Toxicological Profile for Barium and Barium Compounds, ATSDR (Table 4-2, physical and chemical properties)",
        "url": "https://www.atsdr.cdc.gov/ToxProfiles/tp24-c4.pdf",
        "year": 2007,
        "kind": "report",
        "license": "public domain (US government)"
      }
    },
    {
      "benchmark": "melting_point",
      "value": 727,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "pressure": "not stated by source"
      },
      "method": "Value printed in the ATSDR profile",
      "status": "ground",
      "source": "atsdr-2007",
      "where": "Table 4-2, Barium column: Melting point",
      "source_detail": {
        "title": "Toxicological Profile for Barium and Barium Compounds, ATSDR (Table 4-2, physical and chemical properties)",
        "url": "https://www.atsdr.cdc.gov/ToxProfiles/tp24-c4.pdf",
        "year": 2007,
        "kind": "report",
        "license": "public domain (US government)"
      }
    },
    {
      "benchmark": "melting_point",
      "value": 725,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "pressure": "not stated by source"
      },
      "method": "Value printed in the supplier safety data sheet",
      "status": "ground",
      "note": "The supplier sheet gives 725 C, 2 C below the ATSDR value. Both are kept.",
      "source": "aci-ba-sds",
      "where": "Section 9, Melting point/Melting range",
      "source_detail": {
        "title": "Barium safety data sheet, ACI Alloys (Material Name: Barium)",
        "url": "https://www.acialloys.com/wp-content/uploads/msds/ba.html",
        "kind": "datasheet",
        "license": "supplier document"
      }
    },
    {
      "benchmark": "boiling_point",
      "value": 1897,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "pressure": "not stated by source"
      },
      "method": "Value printed in the ATSDR profile",
      "status": "ground",
      "note": "The ATSDR table prints the row label as Boling point. The University of Waterloo page gives the same 1897 C, citing the CRC Handbook 91st edition. The supplier sheet disagrees (1640 C).",
      "source": "atsdr-2007",
      "where": "Table 4-2, Barium column: boiling point row",
      "source_detail": {
        "title": "Toxicological Profile for Barium and Barium Compounds, ATSDR (Table 4-2, physical and chemical properties)",
        "url": "https://www.atsdr.cdc.gov/ToxProfiles/tp24-c4.pdf",
        "year": 2007,
        "kind": "report",
        "license": "public domain (US government)"
      }
    },
    {
      "benchmark": "boiling_point",
      "value": 1640,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "pressure": "not stated by source"
      },
      "method": "Value printed in the supplier safety data sheet",
      "status": "ground",
      "note": "Conflicts with the 1897 C in ATSDR and the Waterloo page. The profile does not choose between them.",
      "source": "aci-ba-sds",
      "where": "Section 9, Boiling point/Boiling range",
      "source_detail": {
        "title": "Barium safety data sheet, ACI Alloys (Material Name: Barium)",
        "url": "https://www.acialloys.com/wp-content/uploads/msds/ba.html",
        "kind": "datasheet",
        "license": "supplier document"
      }
    },
    {
      "benchmark": "electrical_resistivity",
      "value": 34.3,
      "bound": "exact",
      "unit": "microohm cm",
      "scope": "material",
      "conditions": {
        "temperature": "300 K",
        "unit_in_source": "34.3 x 10-8 ohm m"
      },
      "method": "Printed as 34.3 x 10-8 ohm m and converted: 1 microohm cm equals 10-8 ohm m, so the number is unchanged",
      "status": "ground",
      "note": "The page is an aggregator that does not attribute each value to a handbook.",
      "source": "knowledgedoor-barium",
      "where": "Electrical Resistivity (solid) entry at 300 K",
      "source_detail": {
        "title": "Elements handbook: barium (aggregator, cites CRC 88th edition in its references without per-value attribution)",
        "url": "https://www.knowledgedoor.com/2/elements_handbook/barium.html",
        "kind": "database",
        "license": "web page"
      }
    },
    {
      "benchmark": "thermal_conductivity",
      "value": 18.4,
      "bound": "exact",
      "unit": "W/(m·K)",
      "scope": "material",
      "conditions": {
        "temperature": "295 K"
      },
      "method": "Value printed on the page, which marks each thermal conductivity entry as estimated",
      "status": "calculated",
      "source": "knowledgedoor-barium",
      "where": "Thermal Conductivity (solid) entry at 295 K",
      "source_detail": {
        "title": "Elements handbook: barium (aggregator, cites CRC 88th edition in its references without per-value attribution)",
        "url": "https://www.knowledgedoor.com/2/elements_handbook/barium.html",
        "kind": "database",
        "license": "web page"
      }
    },
    {
      "benchmark": "specific_heat",
      "value": 0.204,
      "bound": "exact",
      "unit": "J/(g K)",
      "scope": "material",
      "conditions": {
        "temperature": "298.15 K",
        "pressure": "1 bar"
      },
      "method": "Isobaric specific heat capacity printed on the page",
      "status": "ground",
      "source": "knowledgedoor-barium",
      "where": "Specific heat: Isobaric Specific Heat Capacity row",
      "source_detail": {
        "title": "Elements handbook: barium (aggregator, cites CRC 88th edition in its references without per-value attribution)",
        "url": "https://www.knowledgedoor.com/2/elements_handbook/barium.html",
        "kind": "database",
        "license": "web page"
      }
    },
    {
      "benchmark": "cte",
      "value": 20.6,
      "bound": "exact",
      "unit": "ppm/K",
      "scope": "material",
      "conditions": {
        "temperature": "not stated by source"
      },
      "method": "Printed as 20.6 x 10-6 K-1, which is the same as ppm/K",
      "status": "ground",
      "source": "webelements-physics",
      "where": "Heat and conduction: Coefficient of linear thermal expansion",
      "source_detail": {
        "title": "WebElements: Barium, physical properties",
        "url": "https://www.webelements.com/barium/physics.html",
        "kind": "database",
        "license": "web database"
      }
    },
    {
      "benchmark": "elastic_modulus",
      "value": 13,
      "bound": "exact",
      "unit": "GPa",
      "scope": "material",
      "conditions": {
        "temperature": "not stated by source"
      },
      "method": "Young's modulus printed on the page",
      "status": "ground",
      "source": "webelements-physics",
      "where": "Elastic properties: Young's modulus",
      "source_detail": {
        "title": "WebElements: Barium, physical properties",
        "url": "https://www.webelements.com/barium/physics.html",
        "kind": "database",
        "license": "web database"
      }
    },
    {
      "benchmark": "pauling_electronegativity",
      "label": "Pauling electronegativity",
      "value": 0.89,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "scale": "Pauling"
      },
      "method": "Value printed on the page, which cites the CRC Handbook 91st edition",
      "status": "ground",
      "note": "Not in the canonical property file, so this snake_case name is used. Listed in gaps.",
      "source": "uwaterloo-barium",
      "where": "Atomic properties: Electronegativity",
      "source_detail": {
        "title": "University of Waterloo chemistry page on barium (values cite CRC Handbook of Chemistry and Physics, 91st edition)",
        "url": "https://uwaterloo.ca/chemistry/node/700",
        "kind": "database",
        "license": "web page"
      }
    },
    {
      "benchmark": "first_ionization_energy",
      "label": "First ionization energy",
      "value": 5.211664,
      "bound": "exact",
      "unit": "eV",
      "scope": "material",
      "conditions": {
        "order": "first ionization"
      },
      "method": "Value printed on the page",
      "status": "ground",
      "note": "Not in the canonical property file, so this snake_case name is used. Listed in gaps.",
      "source": "knowledgedoor-barium",
      "where": "Ionization Energies: I (1)",
      "source_detail": {
        "title": "Elements handbook: barium (aggregator, cites CRC 88th edition in its references without per-value attribution)",
        "url": "https://www.knowledgedoor.com/2/elements_handbook/barium.html",
        "kind": "database",
        "license": "web page"
      }
    },
    {
      "benchmark": "enthalpy_of_fusion",
      "label": "Enthalpy of fusion",
      "value": 7.66,
      "bound": "exact",
      "unit": "kJ/mol",
      "scope": "material",
      "conditions": {
        "pressure": "1 atm"
      },
      "method": "Value printed on the page",
      "status": "ground",
      "source": "knowledgedoor-barium",
      "where": "Enthalpy of Fusion entry",
      "source_detail": {
        "title": "Elements handbook: barium (aggregator, cites CRC 88th edition in its references without per-value attribution)",
        "url": "https://www.knowledgedoor.com/2/elements_handbook/barium.html",
        "kind": "database",
        "license": "web page"
      }
    }
  ],
  "corrosion": [
    {
      "environment": "Liquid water",
      "headline": "Barium reacts violently with water and releases flammable hydrogen gas.",
      "effect": "The supplier sheet says barium reacts violently with water and that contact liberates extremely flammable gases. ATSDR says the metal decomposes in water and evolves hydrogen gas.",
      "rating": "severe",
      "conditions": {
        "form": "bulk metal"
      },
      "source": "aci-ba-sds",
      "where": "Section 2 (R14 Reacts violently with water) and Section 10 (Water: reacts violently)"
    },
    {
      "environment": "Moist air",
      "headline": "Barium oxidizes readily in moist air and takes on a silver-yellow colour.",
      "effect": "Metallic barium is silvery-white but takes on a silver-yellow colour when exposed to air. It oxidizes readily in moist air, and in powdered form it reacts violently with air.",
      "rating": "severe",
      "conditions": {
        "atmosphere": "moist air"
      },
      "source": "atsdr-2007",
      "where": "Section 4.2, Physical and chemical properties"
    },
    {
      "environment": "Air, once ignited",
      "headline": "Once ignited, barium burns in air to give barium oxide and barium nitride.",
      "effect": "Once ignited, barium metal burns in air to give a mixture of white barium oxide and barium nitride, Ba3N2.",
      "rating": "severe",
      "conditions": {
        "temperature": "not stated; the page describes ignition only"
      },
      "source": "webelements-chemistry",
      "where": "Reaction of barium with air"
    },
    {
      "environment": "Dry argon",
      "headline": "The supplier recommends handling under dry argon.",
      "effect": "The supplier sheet gives a handling instruction only: handle under dry argon. It states no corrosion rate in dry argon.",
      "rating": "low",
      "conditions": {
        "atmosphere": "dry argon"
      },
      "source": "aci-ba-sds",
      "where": "Section 7, Handling and storage"
    },
    {
      "environment": "Fire-fighting media",
      "headline": "Water, carbon dioxide and halogenated extinguishers are unsuitable for barium fires.",
      "effect": "The supplier sheet lists water, carbon dioxide and halogenated extinguishers as unsuitable. Extinguishing powder is the suitable agent, and contact with water releases hydrogen.",
      "rating": "severe",
      "conditions": {
        "state": "burning or hot barium"
      },
      "source": "aci-ba-sds",
      "where": "Section 5, Fire-fighting measures"
    }
  ],
  "risks": {
    "hazards": [
      {
        "text": "Reacts violently with water. Contact with water liberates extremely flammable gases, and the sheet notes that the released hydrogen is explosive.",
        "ghs": [],
        "source": "aci-ba-sds",
        "where": "Section 2 (R14), Section 5 (Special hazard)"
      },
      {
        "text": "Classified with the old EU irritant symbol Xi. The sheet prints no GHS hazard statement (H-code).",
        "ghs": [],
        "source": "aci-ba-sds",
        "where": "Section 2, Hazard description"
      },
      {
        "text": "UN1400, Barium, hazard class 4.3.",
        "ghs": [],
        "source": "aci-ba-sds",
        "where": "Section 14, Transport information"
      },
      {
        "text": "In powdered form, barium reacts violently with air.",
        "ghs": [],
        "source": "atsdr-2007",
        "where": "Section 4.2, Physical and chemical properties"
      }
    ],
    "failure_risks": [
      {
        "mode": "Barium depletion ends cathode life",
        "trigger": "Evolution and transport of barium away from the emitter surface of a barium-impregnated thermionic cathode",
        "consequence": "NASA Glenn states that this process determines the entitlement lifetime of the cathode.",
        "severity": "high",
        "source": "nasa-kovaleski",
        "where": "Abstract"
      },
      {
        "mode": "Hydrogen release on contact with water",
        "trigger": "Water or moisture reaching bulk barium",
        "consequence": "Liberates extremely flammable gas, which the sheet calls explosive hydrogen.",
        "severity": "high",
        "source": "aci-ba-sds",
        "where": "Section 5 (Special hazard)"
      },
      {
        "mode": "Ignition of powdered barium",
        "trigger": "Powdered barium exposed to air",
        "consequence": "Reacts violently with air, so the powder is a fire hazard.",
        "severity": "high",
        "source": "atsdr-2007",
        "where": "Section 4.2, Physical and chemical properties"
      }
    ],
    "side_effects": [
      {
        "text": "Reaction with water releases hydrogen gas, which can ignite.",
        "affects": "Storage area and fire response",
        "source": "aci-ba-sds",
        "where": "Section 5 and Section 10"
      },
      {
        "text": "Burning barium gives barium oxide and barium nitride as fire residues.",
        "affects": "Fire area",
        "source": "webelements-chemistry",
        "where": "Reaction of barium with air"
      }
    ],
    "handling": [
      {
        "text": "Handle and store under dry argon.",
        "source": "aci-ba-sds"
      },
      {
        "text": "Keep water away. Use extinguishing powder for fires and do not use water.",
        "source": "aci-ba-sds"
      },
      {
        "text": "Ship as UN1400, hazard class 4.3.",
        "source": "aci-ba-sds"
      }
    ],
    "mitigations": [
      {
        "text": "Barium oxide pressed with tungsten in a matrix is the best-performing reservoir cathode material in the NASA Glenn work. The reservoir design aims at more than 100,000 hours of life.",
        "source": "nasa-reservoir",
        "where": "Abstract"
      }
    ]
  },
  "uses": [
    {
      "application": "electronics-and-chips",
      "device": "Getter alloy in an electronic vacuum tube",
      "example": "Barium alloys with aluminium or magnesium are used as getters in electronic tubes to remove residual gases.",
      "source": "atsdr-2007",
      "where": "Section 4.1, Chemical identity"
    },
    {
      "application": "propulsion-and-tanks",
      "device": "Barium-impregnated hollow cathode in ion and Hall thrusters",
      "example": "Hollow cathodes provide electrons for propellant ionization and neutralization in ion and Hall thrusters, and emit electron current in International Space Station plasma contactors.",
      "source": "nasa-kovaleski",
      "where": "Introduction, first paragraph"
    },
    {
      "application": "propulsion-and-tanks",
      "device": "Miniature reservoir dispenser cathode",
      "example": "NASA Glenn and FDE report a miniature reservoir cathode with an objective of more than 100,000 hours of life at high loading.",
      "source": "nasa-reservoir",
      "where": "Abstract"
    },
    {
      "application": "structures",
      "device": "Deoxidizer for steel and other metals",
      "example": "Barium is used as a deoxidizer for steel and other metals.",
      "source": "atsdr-2007",
      "where": "Section 4.1, Chemical identity"
    }
  ],
  "supply": [
    {
      "subject": "Barium, mined as barite (barium sulfate)",
      "abundance": "World barite mine production was 8,700 thousand metric tons in 2025 (rounded total; the United States is withheld). Reserves in thousand metric tons: China 120,000; India 51,000; Iran 100,000; Kazakhstan 85,000; Russia 12,000; Turkey 34,000. Identified barite resources in the United States are 150 million tons. Net import reliance is more than 75 percent. More than 90 percent of barite sold in the United States is a weighting agent in oil and gas drilling fluids. Barium metal is not a separate line in the USGS data.",
      "producers": [
        {
          "country": "India",
          "share_percent": 34.5,
          "year": 2025
        },
        {
          "country": "China",
          "share_percent": 25.3,
          "year": 2025
        },
        {
          "country": "Morocco",
          "share_percent": 11.5,
          "year": 2025
        },
        {
          "country": "Kazakhstan",
          "share_percent": 8,
          "year": 2025
        },
        {
          "country": "Iran",
          "share_percent": 3.4,
          "year": 2025
        },
        {
          "country": "Mexico",
          "share_percent": 3.4,
          "year": 2025
        },
        {
          "country": "Laos",
          "share_percent": 3,
          "year": 2025
        },
        {
          "country": "Turkey",
          "share_percent": 3,
          "year": 2025
        },
        {
          "country": "Russia",
          "share_percent": 2.6,
          "year": 2025
        },
        {
          "country": "Pakistan",
          "share_percent": 1.1,
          "year": 2025
        }
      ],
      "critical_lists": [
        {
          "list": "USGS 2025 final list of critical minerals: barite is listed; barium is not named separately",
          "listed": true
        }
      ],
      "recycling": "No recycling figure for barium was found in the sources read for this profile.",
      "substitutes": [
        "For barite in drilling fluids (USGS): calcium carbonate, hematite, ilmenite and manganese tetroxide."
      ],
      "source": "usgs-barite-2026",
      "where": "Salient statistics and World Mine Production and Reserves table (2025 values); Substitutes section. Shares are computed by the editors as 2025 mine production divided by the rounded world total of 8,700 thousand tons. Critical list status from usgs-critical-2025."
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "Barium safety data sheet (ACI Alloys)",
      "type": "sds",
      "url": "https://www.acialloys.com/wp-content/uploads/msds/ba.html"
    },
    {
      "title": "ATSDR Toxicological Profile for Barium",
      "type": "report",
      "url": "https://www.atsdr.cdc.gov/ToxProfiles/tp24-c4.pdf",
      "year": 2007
    },
    {
      "title": "WebElements: Barium, physical properties",
      "type": "database",
      "url": "https://www.webelements.com/barium/physics.html"
    },
    {
      "title": "WebElements: Barium, chemistry",
      "type": "database",
      "url": "https://www.webelements.com/barium/chemistry.html"
    },
    {
      "title": "University of Waterloo chemistry page on barium (CRC Handbook 91st edition)",
      "type": "database",
      "url": "https://uwaterloo.ca/chemistry/node/700"
    },
    {
      "title": "Elements handbook: barium (aggregator page)",
      "type": "database",
      "url": "https://www.knowledgedoor.com/2/elements_handbook/barium.html"
    },
    {
      "title": "USGS Mineral Commodity Summaries 2026: Barite",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-barite.pdf",
      "year": 2026
    },
    {
      "title": "USGS: Final 2025 list of critical minerals (science snippet)",
      "type": "report",
      "url": "https://www.usgs.gov/news/science-snippet/interior-department-releases-final-2025-list-critical-minerals",
      "year": 2025
    },
    {
      "title": "NASA NTRS 20020013325: Life model of hollow cathodes using a barium calcium aluminate impregnated emitter",
      "type": "report",
      "url": "https://ntrs.nasa.gov/api/citations/20020013325/downloads/20020013325.pdf"
    },
    {
      "title": "NASA NTRS 20020072844: Miniature reservoir cathode, an update (Vancil and Wintucky)",
      "type": "report",
      "url": "https://ntrs.nasa.gov/api/citations/20020072844/downloads/20020072844.pdf"
    }
  ],
  "gaps": [
    "Electrode potential against the standard hydrogen electrode: no source with the number was read in this run.",
    "Specific heat, vapour pressure at room temperature and heat of vaporization: the aggregator page lists them without a handbook attribution, so they are left out apart from specific heat.",
    "Lattice type and space group: the aggregator page gives allotropes and a nearest-neighbour distance (435 pm) but no lattice type. Only cubic is given, from ATSDR.",
    "GHS hazard codes (H-codes) for barium metal: the supplier sheet uses the old EU classification only. No GHS table for barium metal was read in this run.",
    "Health effects and toxicity of the metal and of soluble barium compounds: the ATSDR PDF could not be extracted beyond its physical and chemical section in this run.",
    "Boiling point: sources disagree (1897 C in ATSDR and the Waterloo page citing CRC 91st ed.; 1640 C in the supplier sheet). Not resolved here.",
    "Density: 3.51 g/cm3 (supplier) and 3.62 g/cm3 (ATSDR) disagree. Both are kept and no value is chosen.",
    "Enthalpy of fusion, first ionization energy and Pauling electronegativity are not names in the canonical property file. The snake_case names are used as stated above, and enthalpy_of_fusion is already used in the lithium profile.",
    "Alloying of barium into lead, bearing or aluminium-barium alloys for structural use: no source with compositions was read. Only ATSDR getter alloys with aluminium and magnesium are cited.",
    "Recycled share of barium supply: not read.",
    "Designations (UNS, EN, ASTM and similar codes) for barium metal: none printed by the sources read, so none are listed.",
    "No image with a checked licence was read in this run, so no media entries are included."
  ],
  "story": {
    "why": "Barium is a soft, silvery alkaline earth metal. Because it is so reactive, ATSDR says it does not exist as the metal in the environment. Its useful forms in the sources read are its getter alloys and its oxide. Barium alloys with aluminium or magnesium remove residual gases in electronic vacuum tubes. Barium oxide is pressed into the tungsten emitters of dispenser cathodes, which give electrons for ion and Hall thrusters. The metal must never meet water.",
    "uses": [
      {
        "where": "Electron emitters for electric propulsion",
        "line": "NASA reports that hollow cathodes with barium calcium aluminate impregnated tungsten emitters provide electrons for ion and Hall thrusters, and emit electron current in International Space Station plasma contactors. The lifetime of the cathode is set by the transport of barium away from its emitter surface."
      },
      {
        "where": "Vacuum tubes and getters",
        "line": "Barium alloys with aluminium or magnesium are used as getters in electronic tubes to remove residual gases. Barium is also used as a deoxidizer for steel and other metals."
      }
    ],
    "can_do": [
      {
        "label": "Density",
        "line": "The supplier sheet gives 3.51 g/cm3 at 20 C and ATSDR gives 3.62 g/cm3. The two sources differ, and the profile keeps both.",
        "scope": "material",
        "value": "3.51 g/cm3"
      },
      {
        "label": "Melting point",
        "line": "ATSDR gives 727 C and the supplier sheet 725 C. The heat of fusion is 7.66 kJ/mol, as printed on the aggregator page.",
        "scope": "material",
        "value": "727 °C"
      },
      {
        "label": "Electrical resistivity",
        "line": "Resistivity as printed on the aggregator page, converted from 34.3 x 10-8 ohm m.",
        "scope": "material",
        "value": "34.3 microohm cm at 300 K"
      },
      {
        "label": "Specific heat",
        "line": "Isobaric specific heat capacity at 298.15 K and 1 bar, as printed on the aggregator page.",
        "scope": "material",
        "value": "0.204 J/(g K)"
      }
    ],
    "compare": "Barium is not a battery material, so the collection does not compare it with lithium cells. In the sources read for this profile, barium is used for its getter alloys and for barium oxide in emitters inside sealed vacuum systems. Its two sources give densities of 3.51 and 3.62 g/cm3, and its melting point is 727 C (ATSDR) or 725 C (supplier sheet).",
    "compare_rows": [
      {
        "label": "Density",
        "benchmark": "density",
        "scope": "material"
      },
      {
        "label": "Melting point",
        "benchmark": "melting_point",
        "scope": "material"
      },
      {
        "label": "Electrical resistivity",
        "benchmark": "electrical_resistivity",
        "scope": "material"
      }
    ],
    "handling": [
      "Handle and store under dry argon. Keep it away from water and moist air.",
      "Use extinguishing powder for fires. Water, carbon dioxide and halogenated extinguishers are unsuitable.",
      "Ship as UN1400, hazard class 4.3."
    ],
    "good_for": [
      "Electron emitters in dispenser cathodes, which NASA has used for ion and Hall thrusters.",
      "Getter alloys that remove residual gases in electronic vacuum tubes."
    ],
    "watch_out": [
      "It reacts violently with water and releases flammable hydrogen.",
      "Powdered barium reacts violently with air.",
      "The handbook values for the boiling point do not agree (1897 C and 1640 C), so check a primary table before using it."
    ],
    "verdict": "Barium is a useful getter metal, but it is hazardous to handle. The space uses in the sources read are of barium oxide in emitters inside vacuum hardware, not of bare barium metal.",
    "recipe": {
      "line": "Barium metal is the pure element, Ba, with one atom per formula unit. It is not an alloy in this profile. The supplier sheet says to handle it under dry argon.",
      "parts": [
        {
          "name": "Barium",
          "symbol": "Ba",
          "role": "The only element in the metal. The atomic weight is the value given by ATSDR for the element (molecular weight row, Table 4-2).",
          "atoms": 1,
          "atomic_weight": 137.327
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "The supplier sheet describes barium as reacting violently with water and gives the old EU irritant classification. It prints no GHS hazard codes.",
        "points": [
          {
            "label": "Water reaction",
            "line": "Contact with water releases extremely flammable gas, which the sheet calls explosive hydrogen (R14 and Section 5)."
          },
          {
            "label": "Powder",
            "line": "In powdered form barium reacts violently with air (ATSDR)."
          },
          {
            "label": "Transport",
            "line": "Shipped as UN1400, hazard class 4.3."
          }
        ],
        "level": 3,
        "verdict": "Reacts violently with water; releases hydrogen"
      },
      {
        "title": "Fire",
        "lead": "Burning barium forms oxides and nitrides, and water, carbon dioxide and halogenated extinguishers are unsuitable.",
        "points": [
          {
            "label": "Extinguishing",
            "line": "Extinguishing powder is the suitable agent (Section 5 of the supplier sheet)."
          },
          {
            "label": "Residues",
            "line": "Once ignited, barium burns in air to give barium oxide and barium nitride (WebElements)."
          }
        ],
        "level": 3,
        "verdict": "Use dry powder; never use water"
      },
      {
        "title": "Handling and storage",
        "points": [
          {
            "label": "Storage",
            "line": "Handle and store under dry argon, away from water and moist air (Section 7 of the supplier sheet)."
          },
          {
            "label": "Shipping",
            "line": "Ship as UN1400, hazard class 4.3 (Section 14 of the supplier sheet)."
          }
        ]
      }
    ]
  },
  "updated": "2026-10-26",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 14,
    "unreachable": 2,
    "caveats": 3,
    "note": "Read by an AI assistant on 2026-10-26: 14 property rows from 10 sources. Two melting points, two boiling points and two densities are kept as printed. PubChem and the UNR safety data sheet could not be opened."
  },
  "sources": {
    "aci-ba-sds": {
      "title": "Barium safety data sheet, ACI Alloys (Material Name: Barium)",
      "url": "https://www.acialloys.com/wp-content/uploads/msds/ba.html",
      "kind": "datasheet",
      "license": "supplier document"
    },
    "atsdr-2007": {
      "title": "Toxicological Profile for Barium and Barium Compounds, ATSDR (Table 4-2, physical and chemical properties)",
      "url": "https://www.atsdr.cdc.gov/ToxProfiles/tp24-c4.pdf",
      "year": 2007,
      "kind": "report",
      "license": "public domain (US government)"
    },
    "webelements-physics": {
      "title": "WebElements: Barium, physical properties",
      "url": "https://www.webelements.com/barium/physics.html",
      "kind": "database",
      "license": "web database"
    },
    "webelements-chemistry": {
      "title": "WebElements: Barium, chemistry (reaction with air and water)",
      "url": "https://www.webelements.com/barium/chemistry.html",
      "kind": "database",
      "license": "web database"
    },
    "uwaterloo-barium": {
      "title": "University of Waterloo chemistry page on barium (values cite CRC Handbook of Chemistry and Physics, 91st edition)",
      "url": "https://uwaterloo.ca/chemistry/node/700",
      "kind": "database",
      "license": "web page"
    },
    "knowledgedoor-barium": {
      "title": "Elements handbook: barium (aggregator, cites CRC 88th edition in its references without per-value attribution)",
      "url": "https://www.knowledgedoor.com/2/elements_handbook/barium.html",
      "kind": "database",
      "license": "web page"
    },
    "usgs-barite-2026": {
      "title": "Mineral Commodity Summaries 2026: Barite (USGS)",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-barite.pdf",
      "year": 2026,
      "kind": "report",
      "license": "public domain (US government)"
    },
    "usgs-critical-2025": {
      "title": "USGS: Interior Department releases final 2025 list of critical minerals",
      "url": "https://www.usgs.gov/news/science-snippet/interior-department-releases-final-2025-list-critical-minerals",
      "year": 2025,
      "kind": "web",
      "license": "public domain (US government)"
    },
    "nasa-kovaleski": {
      "title": "Life model of hollow cathodes using a barium calcium aluminate impregnated emitter (NASA Glenn, NTRS 20020013325)",
      "url": "https://ntrs.nasa.gov/api/citations/20020013325/downloads/20020013325.pdf",
      "kind": "report",
      "license": "public domain (US government)"
    },
    "nasa-reservoir": {
      "title": "Miniature Reservoir Cathode, an update (Vancil and Wintucky, FDE Inc. and NASA Glenn, NTRS 20020072844)",
      "url": "https://ntrs.nasa.gov/api/citations/20020072844/downloads/20020072844.pdf",
      "kind": "report",
      "license": "public domain (US government)"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/barium/"
}