spore: profile
id: scandium-oxide
spore_version: 0.2
family: oxide-ceramics
name: Scandium oxide (Sc2O3)
abbreviation: Sc2O3
role: rare-earth oxide for optical coatings, laser ceramics and scandium supply
category: ceramics
type: oxides
summary: |
  Scandium(III) oxide (Sc2O3, CAS 12060-08-1) is a white oxide with a density of 3.86 g/cm3 (Wikipedia infobox). Its melting point is printed as 2,485 °C in Wikipedia and the ProChem safety data sheet, but as 2430 °C in the Ereztech safety data sheet, so both values are kept. Wikipedia calls it the primary form of refined scandium, and the USGS lists scandium on its 2025 critical-mineral list.
best_for: Thin-film optical coatings and high-melting oxide research (Lorad lists thin film coatings as its market focus)
weakest_at: 'Mechanical data are missing from every source we hold: no hardness, strength, toughness or thermal-conductivity figure was recorded'
identity:
  formula: Sc2O3
  cas: 12060-08-1
  space_group: Ia3 (No. 206)
  source: wiki-sc2o3
  where: 'Infobox: crystal structure bixbyite, space group Ia3 (No. 206), CAS Number 12060-08-1, EC number 235-042-0'
tags:
  environments: []
  stresses: []
  applications: []
properties:
  - benchmark: density
    label: Density, reference infobox
    value: 3.86
    unit: g/cm3
    scope: material
    conditions:
      form: compound in the infobox
      temperature: not stated
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wiki-sc2o3
    where: Infobox, Density row
  - benchmark: density
    label: Specific gravity, manufacturer MSDS (2012)
    value: 3.86
    unit: gm/cc
    scope: material
    conditions:
      basis: specific gravity, water = 1, as printed
      form: white powder
    method: Value printed in a 2012 manufacturer material safety data sheet
    status: ground
    source: sam-msds
    where: Section III, Physical/Chemical Characteristics, Specific Gravity row
  - benchmark: density
    label: Specific gravity, supplier SDS (ProChem)
    value: 3.864
    unit: gm/ml
    scope: material
    conditions:
      basis: specific gravity as printed
      form: white powder
    method: Value printed in Section 9 of a supplier safety data sheet
    status: ground
    source: prochem-sds
    where: Section 9, Specific gravity row (printed as SPECIFIC GRAVITY 3.864 gm/ml)
  - benchmark: molar_mass
    label: Molar mass, reference infobox
    value: 137.91
    unit: g/mol
    scope: material
    conditions:
      basis: molar mass of the compound, formula Sc2O3
    method: Value printed in the Wikipedia infobox, printed as 137.910 g/mol
    status: ground
    source: wiki-sc2o3
    where: Infobox, Molar mass row
  - benchmark: melting_point
    label: Melting point, reference infobox
    value: 2485
    unit: °C
    scope: material
    conditions:
      pressure: not stated
      basis: value printed as the melting point of the compound
    method: Value printed in the Wikipedia infobox, which prints 2,485 °C (4,505 °F; 2,758 K)
    status: ground
    source: wiki-sc2o3
    where: Infobox, Melting point row
  - benchmark: melting_point
    label: Melting point, supplier SDS (ProChem)
    value: 2485
    unit: °C
    scope: material
    conditions:
      form: white powder
      pressure: not stated
    method: Value printed in a supplier safety data sheet, Section 9 Physical and Chemical Properties
    status: ground
    source: prochem-sds
    where: Section 9, Melting point row (printed as 2485° C)
  - benchmark: melting_point
    label: Melting point, supplier SDS (Ereztech)
    value: 2430
    unit: °C
    scope: material
    conditions:
      form: solid, white powder
      pressure: not stated
    method: Value printed in Section 9 of a 2025 supplier safety data sheet
    status: ground
    note: This value disagrees with the 2485 °C in Wikipedia and the ProChem SDS. Both values are kept, and neither is averaged.
    source: ereztech-sds
    where: Section 9, Melting Point row (printed as 2430 °C (4406 °F))
  - benchmark: melting_point
    label: Melting point, nanografi product page
    value: 2430
    unit: °C
    scope: material
    conditions:
      form: powder
      note: printed with an approximation sign
    method: Value printed as approximately 2430 °C in the product description table
    status: ground
    note: The page prints this value with an approximation sign, so it is not exact.
    source: nanografi-sc2o3
    where: Product description, Melting point row
  - benchmark: melting_point
    label: Melting point, cited in a 2008 study
    value: 2430
    unit: °C
    scope: material
    conditions:
      basis: approximate value (printed as ~2430°C) quoted from an earlier reference
    method: Value printed in the Introduction of a 2008 paper, which cites an earlier source
    status: ground
    note: Approximate, as printed with a tilde.
    source: joam-2008
    where: Section 1 (Introduction), first paragraph
  - benchmark: refractive_index
    label: Refractive index, bulk (nanografi)
    value: 2
    unit: '-'
    scope: material
    conditions:
      basis: bulk material
      wavelength: 300 nm as printed (A = 300 nm)
    method: Value printed in a supplier product description table, written as nH
    status: ground
    source: nanografi-sc2o3
    where: Product description table, Refractive index (bulk) row
  - benchmark: band_gap
    label: Band gap
    value: 5.7
    unit: eV
    scope: material
    conditions:
      basis: value printed by the supplier; temperature and method not stated
    method: Value printed in a supplier product description table
    status: ground
    source: nanografi-sc2o3
    where: Product description table, Bandgap row
  - benchmark: uv_cutoff
    label: UV cut-off wavelength
    value: 215
    unit: nm
    scope: material
    conditions:
      basis: value printed by the supplier; method not stated
    method: Value printed in a supplier product description table
    status: ground
    source: nanografi-sc2o3
    where: Product description table, UV cut-off row
  - benchmark: lattice_constant
    label: Lattice constant (bixbyite cubic cell)
    value: 985
    unit: pm
    scope: material
    conditions:
      structure: bixbyite, space group Ia3 (No. 206)
      temperature: not stated
    method: Value printed in the Wikipedia infobox
    status: ground
    source: wiki-sc2o3
    where: Infobox, Lattice constant row (printed as a = 985 pm)
corrosion:
  - environment: Water
    headline: Scandium oxide is insoluble in water, per Wikipedia.
    effect: The Wikipedia infobox prints insoluble in water with no exposure time or temperature. No corrosion test on the compound was found.
    rating: none
    conditions:
      basis: solubility statement, no exposure test
    source: wiki-sc2o3
    where: Infobox, Solubility in water row
  - environment: Hot acids
    headline: Scandium oxide dissolves in hot acids with reaction.
    effect: The Wikipedia infobox prints soluble in hot acids (reacts). It gives no acid, concentration or rate, so the severity is unknown.
    rating: unknown
    conditions:
      basis: solubility statement, no acid named
    source: wiki-sc2o3
    where: Infobox, Solubility row
  - environment: Strong oxidizing agents
    headline: The Ereztech SDS lists strong oxidizing agents as incompatible.
    effect: The SDS lists strong oxidizing agents as incompatible materials and excess heat as a condition to avoid. It gives no reaction products or rates.
    rating: unknown
    conditions:
      basis: incompatibility statement in a supplier SDS
    source: ereztech-sds
    where: Section 10, Incompatible Materials and Conditions to Avoid rows
risks:
  hazards:
    - text: PubChem reports that scandium oxide is 'Not Classified' for GHS hazard statements and hazard classes (CID 134661).
      ghs: []
      source: pubchem-sc2o3
      where: Safety and Hazards, GHS Classification
    - text: 'ProChem SDS: ''Not a dangerous substance according to the GHS''. Eye contact may be a mild to severe irritant; skin contact may cause slight to mild irritation; inhaled powder may irritate the respiratory tract.'
      ghs: []
      source: prochem-sds
      where: Section 2, Hazards Identification
    - text: 'Ereztech SDS: not considered hazardous under the 2012 OSHA Hazard Communication Standard (29 CFR 1910.1200). No pictograms and no signal word are required.'
      ghs: []
      source: ereztech-sds
      where: Section 2, Classification and Hazard Pictograms rows
    - text: 'Stanford Advanced Materials MSDS (2012): may cause irritation of the eyes, skin and inhalation route. Chronic inhalation may cause congestion, coughing, granuloma in lungs and hemoglobinemia.'
      ghs: []
      source: sam-msds
      where: Section VI, Health Hazard Data
  failure_risks: []
  side_effects: []
  handling:
    - text: 'Ereztech SDS: store in the original container in a dry, cool and well-ventilated area, away from incompatible materials and food and drink.'
      source: ereztech-sds
      where: Section 7, Safe Storage Conditions
    - text: 'Stanford Advanced Materials MSDS: store in a cool, dry area in a tightly sealed container. Vacuum up spills with a HEPA filter, and take care not to raise dust.'
      source: sam-msds
      where: Sections VII, Steps to be taken in case material is released or spilled
    - text: 'ProChem SDS: handle in an efficient fume hood. If fine dust forms and ventilation is not available, wear a respirator under a respirator protection program.'
      source: prochem-sds
      where: Section 4, Ventilation and Respirator
  mitigations:
    - text: 'ProChem SDS: wear approved safety glasses with side shields, safety goggles or a face shield, and chemical resistant gloves.'
      source: prochem-sds
      where: Section 4, Eye Protection and Skin Protection
uses:
  - application: structures
    device: Aerospace alloys containing scandium
    example: The USGS reports that the principal uses for scandium in 2025 were in aerospace alloys and in solid oxide fuel cells for large-scale power generation and backup power systems. The chapter covers scandium overall, not scandium oxide alone.
    source: usgs-mcs2026-scandium
    where: Domestic Production and Use, first paragraph
  - application: optics-and-cameras
    device: Thin-film optical coatings (electron-beam evaporation source)
    example: Lorad Chemical lists thin film coatings as the market focus for its scandium oxide and e-beam as the evaporation source.
    source: lorad-sc2o3
    where: Product Specifications section, and Product Description section
  - application: optics-and-cameras
    device: Erbium-doped Sc2O3 transparent ceramic (laboratory laser material)
    example: A 2008 study calls cubic sesquioxides, especially scandium oxide, interesting as laser materials because of their very high thermal conductivity. The paper gives a melting point of ~2430°C for Sc2O3, which makes single crystals hard to grow.
    source: joam-2008
    where: Section 1 (Introduction), first column
supply:
  - subject: Scandium (and scandium oxide)
    producers:
      - country: China
        year: 2025
        note: Leading producer of scandium oxide; the USGS prints no share percentage
      - country: Japan
        year: 2025
        note: Refines scandium oxide from Philippine scandium-oxalate feedstock; 89% of 2021 to 2024 US scandium oxide imports came from Japan
      - country: Canada
        year: 2025
        note: Sorel-Tracy operation funded to expand scandium oxide capacity to 9 tons per year
    critical_lists:
      - list: 'USGS 2025 List of Critical Minerals (scandium: used to strengthen metal alloys, in fuel cells and in high-intensity lighting)'
        listed: true
      - list: EU critical raw materials list, Annex II of Regulation (EU) 2024/1252 (entry (ab) scandium)
        listed: true
    recycling: 'USGS: recycling is None.'
    substitutes:
      - 'USGS: titanium and aluminum high-strength alloys, as well as carbon-fiber materials, may substitute in high-performance scandium-alloy applications. In some applications substitution is not possible.'
    source: usgs-mcs2026-scandium
    where: World Mine Production and Reserves (global production about 80 tons and capacity over 90 tons per year in 2025); Events, Trends and Issues (60 tons global consumption in 2025); Recycling; Substitutes; Salient Statistics (2025e price 640 dollars per kilogram for 99.99% powder, 5 to 100 kilogram lots); Import Sources
    note: Scandium oxide price and import shares are USGS figures for the chapter's commodity, not for this exact grade.
  - subject: Scandium oxide price (market reference)
    producers: []
    recycling: 'USGS: recycling is None.'
    substitutes: []
    source: usgs-mcs2026-scandium
    where: 'Salient Statistics table, Scandium oxide, powder, 99.99% purity, 5- to 100-kilogram lot size, 2025e: 640 dollars per kilogram'
documents:
  - title: Ereztech safety data sheet, scandium oxide (SC0081), revision 1.00, date of issue 10/6/2025
    type: sds
    url: https://ereztech.com/wp-content/uploads/chemical_sds/SDS-SC0081.pdf
    year: 2025
  - title: ProChem safety data sheet, scandium (III) oxide, CAS 12060-08-1
    type: sds
    url: https://prochemonline.com/wp-content/uploads/2024/10/3149.ScandiumOxide.pdf
    year: 2024
  - title: Stanford Advanced Materials material safety data sheet, scandium oxide (revision date Sep 5, 2012)
    type: sds
    url: https://www.sputtertargets.net/Public/pdf/scandium-oxide-msds.pdf
    year: 2012
  - title: 'USGS Mineral Commodity Summaries 2026: Scandium'
    type: report
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-scandium.pdf
    year: 2026
  - title: PubChem compound record, scandium oxide (CID 134661)
    type: database
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/134661/JSON
    year: 2026
  - title: Judd-Ofelt analysis of Er3+ absorption intensities in Er3+-doped Sc2O3, Journal of Optoelectronics and Advanced Materials 10(2), 359-362
    type: paper
    url: https://joam.inoe.ro/articles/judd-ofelt-analysis-of-the-er3-4f11-absorption-intensities-in-er3-doped-sc2o3/fulltext
    year: 2008
gaps:
  - 'Thermal conductivity not recorded: the only figure seen is printed on the nanografi page with a garbled unit, so it is left out.'
  - The Lorad Chemical product page could not be read by the value checker, so its density, melting point and refractive index are not recorded as values. The page is cited only for the thin-film market focus and the e-beam evaporation source.
  - Atomic weights of scandium and oxygen were not taken from a fetched source, so the recipe rows carry no atomic_weight.
  - Crustal abundance of scandium was not found in any fetched source.
  - No country share percentages are printed by the USGS chapter; China is named as the leading producer, but no shares are recorded.
  - PubChem's experimental density prints no unit, so it is not recorded as a value.
  - The cation density reported in the 2008 paper is printed in exponent form and is left out.
  - Fracture toughness, hardness, flexural strength, electrical resistivity and dielectric data for sintered Sc2O3 were not found in any fetched source.
  - No failure-mode, ageing or humidity data for Sc2O3 were found, so failure_risks is empty.
  - No flight, vacuum, radiation or space exposure data were found for scandium oxide.
  - Route from Sc2O3 into aluminium-scandium alloys was not read in a fetched source, so it is not recorded.
  - 'Melting point disagrees across sources: 2485 °C (Wikipedia, ProChem SDS) against 2430 °C (Ereztech SDS; nanografi and a 2008 paper give approximate values). All are kept.'
  - 'Non-canonical property names used: molar_mass, band_gap, uv_cutoff and lattice_constant are not in spores/property-canon.yaml.'
  - The transmission range printed by Lorad Chemical was not recorded because its two ends carry different units.
  - No regulatory GHS classification from ECHA was checked; hazard entries rely on PubChem, three supplier documents and a 2012 manufacturer MSDS.
  - Dissolution rate and acid concentration for hot-acid attack were not found; the rating is unknown.
sources:
  lorad-sc2o3:
    title: Scandium Oxide (Sc2O3), Lorad Chemical Corporation product page (catalog SC-4735)
    id: Catalog SC-4735; CAS 12060-08-1
    url: https://loradchemical.com/products/scandium-oxide
    year: 2026
    kind: web
    license: supplier product page, cited not reproduced
  pubchem-sc2o3:
    title: PubChem compound record, scandium oxide (CID 134661)
    id: CID 134661; CAS 12060-08-1
    url: https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/134661/JSON
    year: 2026
    kind: database
    license: public domain (NCBI)
  nanografi-sc2o3:
    title: Scandium Oxide (Sc2O3) Powder, Nanografi product page (SKU NG07RE0104)
    id: SKU NG07RE0104
    url: https://shop.nanografi.com/rare-earth-materials/rare-earth-oxide-powder/scandium-oxide-sc2o3-powder/
    year: 2026
    kind: web
    license: supplier product page, cited not reproduced
  wiki-sc2o3:
    title: Scandium oxide, English Wikipedia article (infobox)
    id: CAS 12060-08-1; EC 235-042-0
    url: https://en.wikipedia.org/wiki/Scandium_oxide
    year: 2026
    kind: web
    license: CC BY-SA 4.0 (Wikipedia)
  usgs-mcs2026-scandium:
    title: 'Mineral Commodity Summaries 2026: Scandium'
    id: USGS MCS 2026, February 2026
    url: https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-scandium.pdf
    year: 2026
    kind: report
    license: public domain (USGS)
  usgs-crit2025:
    title: About the 2025 List of Critical Minerals (USGS final list)
    id: Final 2025 List of Critical Minerals, November 2025
    url: https://www.usgs.gov/programs/mineral-resources-program/science/about-2025-list-critical-minerals
    year: 2025
    kind: web
    license: public domain (USGS)
  joam-2008:
    title: Judd-Ofelt analysis of the Er3+ (4f11) absorption intensities in Er3+-doped Sc2O3
    id: Journal of Optoelectronics and Advanced Materials, Vol. 10, No. 2, February 2008, p. 359-362
    url: https://joam.inoe.ro/articles/judd-ofelt-analysis-of-the-er3-4f11-absorption-intensities-in-er3-doped-sc2o3/fulltext
    year: 2008
    kind: paper
    license: open-access journal (licence not read on the page)
  eu-annex2:
    title: List of 34 Critical Raw Materials, Annex II of the Critical Raw Materials Act 2023 (copy hosted by EIT RawMaterials)
    id: Regulation (EU) 2024/1252, Annex II
    url: https://eitrawmaterials.eu/sites/default/files/2026-02/List%20of%2034%20Critical%20Raw%20Materials%20Annex%20II%20CRMA%202023.pdf
    year: 2024
    kind: standard
    license: EU legislation, cited not reproduced
  ec-crm:
    title: Critical raw materials, European Commission page
    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
  prochem-sds:
    title: Scandium (III) oxide safety data sheet, ProChem Inc., CAS 12060-08-1
    id: CAS 12060-08-1; date prepared 04/14 as printed
    url: https://prochemonline.com/wp-content/uploads/2024/10/3149.ScandiumOxide.pdf
    year: 2024
    kind: datasheet
    license: supplier document, linked not reproduced
  ereztech-sds:
    title: Scandium oxide safety data sheet, Ereztech LLC, SC0081, revision 1.00
    id: Ereztech SC0081; CAS 12060-08-1; date of issue 10/6/2025
    url: https://ereztech.com/wp-content/uploads/chemical_sds/SDS-SC0081.pdf
    year: 2025
    kind: datasheet
    license: supplier document, linked not reproduced
  sam-msds:
    title: Material Safety Data Sheet, Scandium Oxide, Stanford Advanced Materials (version 2.0)
    id: CAS 12060-08-1; revision date Sep 5, 2012
    url: https://www.sputtertargets.net/Public/pdf/scandium-oxide-msds.pdf
    year: 2012
    kind: datasheet
    license: supplier document, linked not reproduced
license: CC-BY-4.0
updated: '2026-11-01'
review:
  status: draft
  method: assistant
  checked_values: 13
  unreachable: 0
  caveats: 1
  note: Values read on 2026-11-01 from pages fetched in this run. Melting-point values disagree across sources and all are kept. Thermal conductivity, atomic weights and crustal abundance are left out (see gaps).
story:
  recipe:
    line: 'Sc2O3 is scandium(III) oxide: two scandium atoms and three oxygen atoms per formula unit, in a bixbyite (cubic) crystal with space group Ia3 (No. 206) and a lattice constant of 985 pm (Wikipedia infobox). Scandium is produced as a byproduct, mainly from nickel and titanium process streams; scandium materials are also produced in the Philippines and sent to Japan for processing into scandium oxide (USGS).'
    parts:
      - name: Scandium
        symbol: Sc
        role: The metal in the oxide. Scandium is produced as a byproduct of nickel and titanium processing, so supply depends on those industries (USGS).
      - name: Oxygen
        symbol: O
        role: Forms the oxide framework. Wikipedia calls scandium oxide the primary form of refined scandium.
  risk_groups:
    - title: For people
      level: 0
      verdict: Not classified as hazardous under GHS by PubChem
      lead: PubChem lists no GHS hazard class for the compound, and the 2025 Ereztech SDS says it is not hazardous under the 2012 OSHA standard. Two supplier documents still describe irritation.
      points:
        - label: Eyes and skin
          line: The ProChem SDS says the powder may be a mild to severe irritant to the eyes and may cause slight to mild skin irritation.
        - label: Inhaled dust
          line: The 2012 Stanford Advanced Materials MSDS lists irritation of the airways and, after chronic exposure, granuloma in the lungs.
    - title: Storage and handling
      points:
        - label: Incompatible materials
          line: The Ereztech SDS lists strong oxidizing agents as incompatible (Section 10).
        - label: Dust
          line: Avoid raising dust. Use a fume hood, and a respirator for fine dust when ventilation is poor (ProChem SDS, Section 4).
  why: Scandium(III) oxide (Sc2O3, CAS 12060-08-1) is a white oxide of scandium. Wikipedia says it is the primary form of refined scandium produced by the mining industry. Its melting point is printed as 2,485 °C in the Wikipedia infobox. The USGS names aerospace alloys and solid oxide fuel cells as the principal uses of scandium in 2025, and lists scandium as critical in the US 2025 list and in the EU Annex II list. The oxide is also sold for thin-film optical coatings (Lorad Chemical).
  uses:
    - where: Aerospace alloys and fuel cells
      line: The USGS reports that the principal uses for scandium in 2025 were in aerospace alloys and in solid oxide fuel cells for large-scale power generation and backup power systems. The chapter covers scandium overall, not scandium oxide alone.
    - where: Thin-film optical coatings
      line: Lorad Chemical lists thin film coatings as the market focus for scandium oxide and e-beam as the evaporation source.
    - where: Laser ceramics (laboratory)
      line: A 2008 study calls scandium oxide interesting as a laser material because of its very high thermal conductivity. The same paper gives a melting point of about 2430 °C, which makes single crystals hard to grow, so transparent ceramics are used instead.
  can_do:
    - label: Melting point
      line: Melts at 2,485 °C in the Wikipedia infobox, although the Ereztech SDS prints 2430 °C for the same compound.
    - label: Optical use
      line: Lorad Chemical and nanografi both describe the oxide's optical properties, which suit thin-film optical coatings.
    - label: Band gap
      line: Has a band gap of 5.7 eV and a UV cut-off of 215 nm (nanografi).
    - label: Density
      line: Has a density of 3.86 g/cm3 in the Wikipedia infobox and 3.86 gm/cc in a 2012 manufacturer MSDS.
  compare: Scandium oxide is a refractory oxide, and the sources we hold give optical and thermal-stability data rather than mechanical data. Alumina in this collection is the closest comparison, a hard insulating oxide ceramic, but no strength or toughness figure for scandium oxide was found to set beside alumina's. Its melting point of 2,485 °C in Wikipedia is listed as 2430 °C in an SDS, so the two values are shown side by side rather than averaged.
  compare_rows:
    - label: Melting point
      benchmark: melting_point
    - label: Density
      benchmark: density
    - label: Refractive index
      benchmark: refractive_index
  handling:
    - Keep the container tightly sealed in a cool, dry, well-ventilated place, away from strong oxidizing agents (Ereztech and SAM documents).
    - Avoid raising dust. Use a fume hood, and a respirator for fine dust when ventilation is poor (ProChem SDS).
    - Wear safety glasses with side shields and chemical-resistant gloves (ProChem SDS).
  good_for:
    - Thin-film optical coatings, the market Lorad Chemical lists for its scandium oxide.
    - Research on transparent ceramic laser hosts, where the cubic oxide's high thermal conductivity is the stated attraction (2008 study).
  watch_out:
    - 'Melting point values disagree between sources: 2,485 °C (Wikipedia, ProChem SDS) and 2430 °C (Ereztech SDS).'
    - Single crystals are hard to grow because of the high melting point (2008 study), so transparent ceramics are used instead.
    - The 2012 manufacturer MSDS lists chronic lung and blood effects from inhaled dust, while most newer SDSs report no GHS class.
  verdict: Scandium oxide is a dense, refractory oxide with useful optical data. Its mechanical data are missing from the sources we hold, and its melting point is reported two ways.