{
  "spore": "profile",
  "id": "n-hexadecane-pcm",
  "spore_version": "0.2",
  "family": "paraffins",
  "name": "n-Hexadecane (paraffin phase change material)",
  "role": "phase change material for passive thermal control",
  "category": "thermal-protection",
  "type": "multi-layer-insulation",
  "summary": "n-Hexadecane (C16H34) is a straight-chain alkane that melts at 18.18 °C and stores heat as latent heat while it melts. Three mini-packs holding 40.69 g of it flew on the IceCube 3U CubeSat in low Earth orbit, and NASA reports that the instrument stayed near 18 °C most of the time. PubChem's hazard data give an aspiration hazard (H304), and sources disagree on the flash point (135 °C and 136 °C).\n",
  "best_for": "Passive temperature hold near 18 °C in a small spacecraft instrument, as flown on IceCube (NASA)",
  "weakest_at": "Combustibility and an aspiration hazard (H304 in PubChem's ECHA notifications); no ageing or thermal-conductivity data found",
  "identity": {
    "formula": "C16H34",
    "cas": "544-76-3",
    "designations": [],
    "source": "wikipedia-hexadecane",
    "where": "Lead and infobox: chemical formula C16H34 and CAS number 544-76-3 (PubChem CID 11006 gives the same CAS)"
  },
  "tags": {
    "environments": [
      "low-earth-orbit"
    ],
    "stresses": [
      "thermal-cycling"
    ],
    "applications": [
      "thermal-control"
    ]
  },
  "properties": [
    {
      "benchmark": "melting_point",
      "label": "Melting point, Tfus (NIST phase change data)",
      "value": 291,
      "bound": "exact",
      "unit": "K",
      "scope": "material",
      "conditions": {
        "basis": "average of 52 out of 54 values, as printed by NIST"
      },
      "method": "Phase change data table, average of measured values",
      "status": "ground",
      "uncertainty": "± 1 K",
      "source": "nist-webbook",
      "where": "Phase change data table, row Tfus",
      "source_detail": {
        "title": "NIST Chemistry WebBook: hexadecane, phase change data",
        "id": "CAS 544-76-3; NIST Standard Reference Database 69",
        "url": "https://webbook.nist.gov/cgi/cbook.cgi?Mask=4&ID=C544763",
        "kind": "database",
        "license": "US government data"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point (CRC Handbook value printed on PubChem)",
      "value": 18.18,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "basis": "CRC Handbook value as printed on PubChem"
      },
      "method": "Printed on the PubChem record as the CRC Handbook value",
      "status": "ground",
      "source": "pubchem-hexadecane",
      "where": "3.2.5 Melting Point, first entry",
      "source_detail": {
        "title": "PubChem compound record, Hexadecane (CID 11006)",
        "id": "CID 11006; CAS 544-76-3",
        "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Hexadecane",
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point of the PCM as flown (NASA)",
      "value": 18,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "use": "paraffin PCM mini-packs on IceCube",
        "mass": "40.69 g n-Hexadecane"
      },
      "method": "Stated in the NASA paper's description of the paraffin PCM",
      "status": "ground",
      "source": "nasa-ntrs-pcm",
      "where": "Section II (Why Paraffin PCM is Flown on IceCube Instrument), paragraph on the paraffin",
      "source_detail": {
        "title": "Thermal Assessment of Paraffin Phase Change Material Mini-Packs on IceCube 3U CubeSat in Flight",
        "id": "Choi, AIAA Propulsion and Energy Forum 2018, GSFC-E-DAA-TN54685, NTRS 20180004470",
        "url": "https://ntrs.nasa.gov/citations/20180004470",
        "year": 2018,
        "kind": "paper",
        "license": "NASA public document"
      }
    },
    {
      "benchmark": "boiling_point",
      "label": "Boiling point, Tboil (NIST)",
      "value": 554,
      "bound": "exact",
      "unit": "K",
      "scope": "material",
      "conditions": {
        "basis": "average of 10 values, as printed by NIST"
      },
      "method": "Phase change data table, average of measured values",
      "status": "ground",
      "uncertainty": "± 10 K",
      "source": "nist-webbook",
      "where": "Phase change data table, row Tboil",
      "source_detail": {
        "title": "NIST Chemistry WebBook: hexadecane, phase change data",
        "id": "CAS 544-76-3; NIST Standard Reference Database 69",
        "url": "https://webbook.nist.gov/cgi/cbook.cgi?Mask=4&ID=C544763",
        "kind": "database",
        "license": "US government data"
      }
    },
    {
      "benchmark": "critical_temperature",
      "label": "Critical temperature, Tc (NIST)",
      "value": 722,
      "bound": "exact",
      "unit": "K",
      "scope": "material",
      "conditions": {
        "basis": "average of 9 values, as printed by NIST"
      },
      "method": "Phase change data table, average of measured values",
      "status": "ground",
      "uncertainty": "± 4 K",
      "source": "nist-webbook",
      "where": "Phase change data table, row Tc",
      "source_detail": {
        "title": "NIST Chemistry WebBook: hexadecane, phase change data",
        "id": "CAS 544-76-3; NIST Standard Reference Database 69",
        "url": "https://webbook.nist.gov/cgi/cbook.cgi?Mask=4&ID=C544763",
        "kind": "database",
        "license": "US government data"
      }
    },
    {
      "benchmark": "density",
      "label": "Density (CRC Handbook value printed on PubChem)",
      "value": 0.7701,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "temperature": "25 °C",
        "printed_unit": "g/cu cm"
      },
      "method": "Printed on the PubChem record as the CRC Handbook value at 25 °C",
      "status": "ground",
      "source": "pubchem-hexadecane",
      "where": "3.2.8 Density, entry citing Haynes, CRC Handbook 95th ed.",
      "source_detail": {
        "title": "PubChem compound record, Hexadecane (CID 11006)",
        "id": "CID 11006; CAS 544-76-3",
        "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Hexadecane",
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "flash_point",
      "label": "Flash point, closed cup (PubChem, citing a Sigma-Aldrich SDS)",
      "value": 135,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "test_method": "closed cup",
        "printed_value": "135 °C (275 °F) - closed cup"
      },
      "method": "Printed on the PubChem record, which cites a Sigma-Aldrich safety data sheet (product 52209); that SDS was not read directly",
      "status": "ground",
      "source": "pubchem-hexadecane",
      "where": "3.2.6 Flash Point, closed cup entry",
      "source_detail": {
        "title": "PubChem compound record, Hexadecane (CID 11006)",
        "id": "CID 11006; CAS 544-76-3",
        "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Hexadecane",
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "flash_point",
      "label": "Flash point (Wikipedia infobox)",
      "value": 136,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "printed_value": "136 °C (277 °F; 409 K)",
        "test_method": "not stated"
      },
      "method": "Printed in the Wikipedia infobox; the test method is not given",
      "status": "ground",
      "note": "Differs by one degree from the PubChem closed-cup value; both are recorded and the test method is not stated for this one.",
      "source": "wikipedia-hexadecane",
      "where": "Infobox, flash point row",
      "source_detail": {
        "title": "Hexadecane, Wikipedia",
        "id": "Hexadecane article, lead and infobox",
        "url": "https://en.wikipedia.org/wiki/Hexadecane",
        "kind": "web",
        "license": "CC BY-SA 4.0, linked not reproduced"
      }
    },
    {
      "benchmark": "refractive_index",
      "label": "Refractive index (n_D)",
      "value": 1.4329,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "temperature": "25 °C",
        "wavelength": "not stated"
      },
      "method": "Printed on the PubChem record as the CRC Handbook value",
      "status": "ground",
      "source": "pubchem-hexadecane",
      "where": "3.2.18 Refractive Index",
      "source_detail": {
        "title": "PubChem compound record, Hexadecane (CID 11006)",
        "id": "CID 11006; CAS 544-76-3",
        "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Hexadecane",
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "dynamic_viscosity",
      "label": "Dynamic viscosity",
      "value": 3.474,
      "bound": "exact",
      "unit": "mPa s",
      "scope": "material",
      "conditions": {
        "temperature": "20 °C"
      },
      "method": "Printed on the PubChem record, citing Ullmann's Encyclopedia of Industrial Chemistry",
      "status": "ground",
      "source": "pubchem-hexadecane",
      "where": "3.2.14 Viscosity",
      "source_detail": {
        "title": "PubChem compound record, Hexadecane (CID 11006)",
        "id": "CID 11006; CAS 544-76-3",
        "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Hexadecane",
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "enthalpy_of_vaporization",
      "label": "Enthalpy of vaporization at standard conditions (NIST)",
      "value": 81.3,
      "bound": "exact",
      "unit": "kJ/mol",
      "scope": "material",
      "conditions": {
        "basis": "average of 9 values; standard conditions per NIST notes"
      },
      "method": "Phase change data table, average of measured values",
      "status": "ground",
      "uncertainty": "± 0.6 kJ/mol",
      "source": "nist-webbook",
      "where": "Phase change data table, row ΔvapH°",
      "source_detail": {
        "title": "NIST Chemistry WebBook: hexadecane, phase change data",
        "id": "CAS 544-76-3; NIST Standard Reference Database 69",
        "url": "https://webbook.nist.gov/cgi/cbook.cgi?Mask=4&ID=C544763",
        "kind": "database",
        "license": "US government data"
      }
    },
    {
      "benchmark": "latent_heat_of_fusion",
      "label": "Enthalpy of fusion (NASA)",
      "value": 235,
      "bound": "exact",
      "unit": "kJ/kg",
      "scope": "material",
      "conditions": {
        "basis": "as quoted by NASA with its handbook references"
      },
      "method": "Stated in the NASA paper, which cites earlier handbooks and a company report",
      "status": "ground",
      "source": "nasa-ntrs-pcm",
      "where": "Section II, paragraph on the paraffin",
      "source_detail": {
        "title": "Thermal Assessment of Paraffin Phase Change Material Mini-Packs on IceCube 3U CubeSat in Flight",
        "id": "Choi, AIAA Propulsion and Energy Forum 2018, GSFC-E-DAA-TN54685, NTRS 20180004470",
        "url": "https://ntrs.nasa.gov/citations/20180004470",
        "year": 2018,
        "kind": "paper",
        "license": "NASA public document"
      }
    },
    {
      "benchmark": "enthalpy_of_fusion",
      "label": "Enthalpy of fusion, DSC (NIST list)",
      "value": 53,
      "bound": "exact",
      "unit": "kJ/mol",
      "scope": "material",
      "conditions": {
        "temperature": "290.7 K",
        "method_as_printed": "DSC"
      },
      "method": "Printed in the NIST enthalpy of fusion list, row Mondieig, Rajabalee, et al., 2004",
      "status": "ground",
      "source": "nist-webbook",
      "where": "Enthalpy of fusion list, row Mondieig, Rajabalee, et al., 2004",
      "source_detail": {
        "title": "NIST Chemistry WebBook: hexadecane, phase change data",
        "id": "CAS 544-76-3; NIST Standard Reference Database 69",
        "url": "https://webbook.nist.gov/cgi/cbook.cgi?Mask=4&ID=C544763",
        "kind": "database",
        "license": "US government data"
      }
    },
    {
      "benchmark": "molar_heat_capacity_liquid",
      "label": "Constant-pressure heat capacity of the liquid (NIST, Costas, Huu, et al., 1988)",
      "value": 500.21,
      "bound": "exact",
      "unit": "J/mol*K",
      "scope": "material",
      "conditions": {
        "temperature": "298.15 K",
        "pressure": "not stated",
        "phase": "liquid"
      },
      "method": "Printed in the NIST liquid heat capacity table; other rows in that table differ slightly",
      "status": "ground",
      "source": "nist-webbook-cp",
      "where": "Constant pressure heat capacity of liquid table, row Costas, Huu, et al., 1988",
      "source_detail": {
        "title": "NIST Chemistry WebBook: hexadecane, condensed phase thermochemistry (constant-pressure heat capacity of liquid)",
        "id": "CAS 544-76-3; NIST Standard Reference Database 69",
        "url": "https://webbook.nist.gov/cgi/cbook.cgi?ID=C544763&Units=SI&Mask=2",
        "kind": "database",
        "license": "US government data"
      }
    },
    {
      "benchmark": "autoignition_temperature",
      "label": "Autoignition temperature",
      "value": 202,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "printed_value": "396 °F (202 °C)"
      },
      "method": "Printed on the PubChem record, citing the NFPA Fire Protection Guide to Hazardous Materials, 14th ed.",
      "status": "ground",
      "source": "pubchem-hexadecane",
      "where": "3.2.12 Autoignition Temperature, second entry",
      "source_detail": {
        "title": "PubChem compound record, Hexadecane (CID 11006)",
        "id": "CID 11006; CAS 544-76-3",
        "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Hexadecane",
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "latent_heat_storage",
      "label": "Latent heat stored by the flown PCM mass",
      "value": 9.562,
      "bound": "exact",
      "unit": "kJ",
      "scope": "material",
      "conditions": {
        "mass": "40.69 g n-Hexadecane",
        "form": "PCM mini-packs flown on IceCube"
      },
      "method": "Stated in the NASA paper as the thermal energy the PCM can store as latent heat",
      "status": "calculated",
      "source": "nasa-ntrs-pcm",
      "where": "Section II, paragraph on the PCM mass",
      "source_detail": {
        "title": "Thermal Assessment of Paraffin Phase Change Material Mini-Packs on IceCube 3U CubeSat in Flight",
        "id": "Choi, AIAA Propulsion and Energy Forum 2018, GSFC-E-DAA-TN54685, NTRS 20180004470",
        "url": "https://ntrs.nasa.gov/citations/20180004470",
        "year": 2018,
        "kind": "paper",
        "license": "NASA public document"
      }
    },
    {
      "benchmark": "instrument_temperature_in_flight",
      "label": "Instrument temperature held by the PCM in flight",
      "value": 18,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "platform": "IceCube 3U CubeSat instrument in ISS orbit",
        "period": "day of year 250 to 255 in 2017",
        "condition": "most of the time, as printed"
      },
      "method": "Flight temperature telemetry reported in the NASA paper",
      "status": "flight",
      "source": "nasa-ntrs-pcm",
      "where": "Abstract",
      "source_detail": {
        "title": "Thermal Assessment of Paraffin Phase Change Material Mini-Packs on IceCube 3U CubeSat in Flight",
        "id": "Choi, AIAA Propulsion and Energy Forum 2018, GSFC-E-DAA-TN54685, NTRS 20180004470",
        "url": "https://ntrs.nasa.gov/citations/20180004470",
        "year": 2018,
        "kind": "paper",
        "license": "NASA public document"
      }
    }
  ],
  "corrosion": [
    {
      "environment": "Repeated melting and freezing (organic PCMs in general)",
      "headline": "Repeated phase changes can degrade organic PCMs; no cycling test on n-hexadecane was found.",
      "effect": "Wikipedia states that repeated phase transitions can lead to material degradation in the case of organic PCMs. No cycling or ageing result for n-hexadecane was found in the sources read.",
      "rating": "unknown",
      "conditions": {
        "basis": "general statement about organic PCMs, not a test on this grade"
      },
      "source": "wikipedia-phase-change-material",
      "where": "Phase-change material article, organic PCM discussion"
    },
    {
      "environment": "Flight melting and freezing on IceCube (ISS orbit)",
      "headline": "The flown mini-packs cycled through melting and freezing and were reported functional.",
      "effect": "NASA reports that the flight results validated the functionality of the paraffin PCM mini-packs. The paper reports no chemical change or loss of latent heat for n-hexadecane after flight.",
      "rating": "unknown",
      "conditions": {
        "platform": "IceCube 3U CubeSat, ISS orbit",
        "period": "day of year 250 to 255 in 2017"
      },
      "source": "nasa-ntrs-pcm",
      "where": "Final paragraphs of the paper, concluding discussion"
    },
    {
      "environment": "Heating to decomposition",
      "headline": "Heated to decomposition, it gives off acrid smoke and irritating vapors.",
      "effect": "PubChem, quoting Sax's Dangerous Properties of Industrial Materials, states that when heated to decomposition hexadecane emits acrid smoke and irritating vapors. No decomposition temperature was found.",
      "rating": "unknown",
      "conditions": {
        "basis": "qualitative statement, no temperature given"
      },
      "source": "pubchem-hexadecane",
      "where": "3.2.13 Decomposition"
    }
  ],
  "risks": {
    "hazards": [
      {
        "text": "PubChem's ECHA-based summary gives GHS H304 for 96.9% of notifications: May be fatal if swallowed and enters airways. Signal word Danger. PubChem also notes it does not meet GHS hazard criteria for 0.1% (2 of 1815) of reports.",
        "ghs": [
          "H304"
        ],
        "source": "pubchem-hexadecane",
        "where": "11.1.1 GHS Classification"
      },
      {
        "text": "PubChem gives the NFPA 704 rating for hexadecane as health 1, fire 1 and instability 0.",
        "ghs": [],
        "source": "pubchem-hexadecane",
        "where": "11.1.3 NFPA Hazard Classification"
      },
      {
        "text": "PubChem records both 'Flammable' and 'Combustible' for hexadecane, both from NTP (1992).",
        "ghs": [],
        "source": "pubchem-hexadecane",
        "where": "11.1.4 Health Hazards and 11.1.5 Fire Hazards"
      },
      {
        "text": "Skin irritation is recorded inconsistently: PubChem quotes Sax's Dangerous Properties calling hexadecane a severe human skin irritant, and Patty's Toxicology calling it a mild eye and mucous membrane irritant and primary skin irritant.",
        "ghs": [],
        "source": "pubchem-hexadecane",
        "where": "11.1.7 Skin, Eye, and Respiratory Irritations"
      }
    ],
    "failure_risks": [
      {
        "mode": "PCM mass too small for the operation scheme",
        "trigger": "The Day-On/Night-Off operation scheme in flight, which had large deviations from the pre-launch design power-on time for the 40.69 g PCM",
        "consequence": "NASA states the mass of the paraffin is not adequate for this operation scheme.",
        "severity": "moderate",
        "source": "nasa-ntrs-pcm",
        "where": "Thermal energy balance discussion of the Day-On/Night-Off scheme"
      }
    ],
    "side_effects": [
      {
        "text": "When heated to decomposition, hexadecane emits acrid smoke and irritating vapors (Sax, quoted by PubChem).",
        "affects": "People near a fire or overheated container",
        "source": "pubchem-hexadecane",
        "where": "3.2.13 Decomposition"
      }
    ],
    "handling": [
      {
        "text": "PubChem's first-aid text for hexadecane says: DO NOT INDUCE VOMITING.",
        "source": "pubchem-hexadecane",
        "where": "11.3.1 First Aid, ingestion entry (NTP, 1992)"
      },
      {
        "text": "PubChem quotes a Sigma-Aldrich safety data sheet (product 52209) as stating: Stable under recommended storage conditions.",
        "source": "pubchem-hexadecane",
        "where": "3.2.11 Stability / Shelf Life"
      }
    ],
    "mitigations": []
  },
  "uses": [
    {
      "application": "thermal-control",
      "device": "Paraffin PCM mini-packs on the IceCube 3U CubeSat instrument",
      "example": "Three paraffin phase change material mini-packs were flown on the IceCube instrument in the International Space Station (ISS) orbit. They contained a total of 40.69 g of n-Hexadecane.",
      "source": "nasa-ntrs-pcm",
      "where": "Abstract"
    },
    {
      "application": "thermal-control",
      "device": "Latent-heat storage in the IceCube instrument (flight design)",
      "example": "The paper states that the PCM is capable of storing 9.562 kJ of thermal energy as latent heat.",
      "source": "nasa-ntrs-pcm",
      "where": "Section II (Why Paraffin PCM is Flown on IceCube Instrument)"
    }
  ],
  "supply": [
    {
      "subject": "Paraffin feedstock (petroleum slack wax), the general source of paraffin",
      "abundance": "Not stated for n-hexadecane; the Wikipedia article describes the feedstock for paraffin wax in general",
      "producers": [],
      "critical_lists": [],
      "recycling": "Not described in the source read",
      "substitutes": [],
      "source": "wikipedia-paraffin-wax",
      "where": "Sourcing and refining section: paraffin is derived from petroleum, coal, or oil shale, and the feedstock is slack wax"
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "NIST Chemistry WebBook: hexadecane, phase change data",
      "type": "database",
      "url": "https://webbook.nist.gov/cgi/cbook.cgi?Mask=4&ID=C544763"
    },
    {
      "title": "PubChem: Hexadecane (CID 11006), GHS classification and physical properties",
      "type": "database",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Hexadecane"
    },
    {
      "title": "Choi, Thermal Assessment of Paraffin Phase Change Material Mini-Packs on IceCube 3U CubeSat in Flight (AIAA 2018)",
      "type": "paper",
      "url": "https://ntrs.nasa.gov/citations/20180004470",
      "year": 2018
    },
    {
      "title": "NIST Atomic Weights and Isotopic Compositions: carbon",
      "type": "database",
      "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=C&all=all&ascii=html"
    }
  ],
  "gaps": [
    "No thermal cycling or long-term ageing test on n-hexadecane was found in the sources read; the only in-flight result is a single period from day of year 250 to 255 in 2017.",
    "Thermal conductivity of n-hexadecane, solid or liquid, was not found in any source read.",
    "Specific heat in J/(kg K) was not found: NIST gives only a molar heat capacity, recorded as molar_heat_capacity_liquid.",
    "Outgassing, total mass loss, radiation and atomic oxygen data for n-hexadecane in vacuum were not found.",
    "Producer shares and the production route for n-hexadecane were not found; the supply entry covers paraffin feedstock in general from Wikipedia.",
    "The Sigma-Aldrich safety data sheet (product 52209) was not read; its flash point and stability statements are cited through PubChem.",
    "The HSDB record (captcha) and ChemIDplus (connection reset) could not be read in this run, so their values are not recorded.",
    "Benchmark names not in the canonical list: latent_heat_of_fusion, enthalpy_of_fusion, enthalpy_of_vaporization, molar_heat_capacity_liquid, critical_temperature, autoignition_temperature, dynamic_viscosity, latent_heat_storage, instrument_temperature_in_flight.",
    "No taxonomy type fits a phase change material; multi-layer-insulation is the nearest passive thermal-control type.",
    "NIST gives standard atomic weights as intervals, so no single atomic weight is recorded for carbon or hydrogen."
  ],
  "story": {
    "why": "n-Hexadecane is a phase change material (PCM): a substance that absorbs or releases large amounts of heat when it changes phase, here solid to liquid at about 18 °C. It is also called cetane, and Wikipedia gives it a cetane number of 100. NASA flew three mini-packs holding 40.69 g of it on the IceCube 3U CubeSat in ISS orbit, and the instrument stayed near 18 °C most of the time.",
    "uses": [
      {
        "where": "Thermal control on a CubeSat",
        "line": "NASA flew three paraffin mini-packs holding 40.69 g of n-Hexadecane in total on the IceCube instrument. The paper says the latent heat change maintained the instrument temperature at about 18 °C most of the time."
      },
      {
        "where": "Latent-heat storage",
        "line": "Per NASA, the 40.69 g PCM mass stores 9.562 kJ of thermal energy as latent heat."
      }
    ],
    "can_do": [
      {
        "label": "Melting point",
        "line": "The CRC Handbook value printed on PubChem is 18.18 °C. NIST gives 291 K for the same transition.",
        "benchmark": "melting_point",
        "scope": "material",
        "value": "18.18 °C"
      },
      {
        "label": "Stored heat",
        "line": "Per NASA, 40.69 g stores 9.562 kJ as latent heat. NASA quotes an enthalpy of fusion of 235 kJ/kg.",
        "benchmark": "latent_heat_storage",
        "scope": "material",
        "value": "9.562 kJ"
      },
      {
        "label": "Flight hold",
        "line": "In flight on IceCube, from day of year 250 to 255 in 2017, the instrument temperatures stayed near 18 °C most of the time.",
        "benchmark": "instrument_temperature_in_flight",
        "scope": "material",
        "value": "about 18 °C"
      }
    ],
    "compare": "n-Hexadecane is one defined alkane, which is not the same as paraffin wax. Paraffin wax is a mixture of hydrocarbons with a range of chain lengths (Wikipedia), so its melting range is wider and its values are not used here. The table lists the melting point, density and latent heat of fusion recorded for this grade.",
    "compare_rows": [
      {
        "label": "Melting point",
        "benchmark": "melting_point",
        "scope": "material"
      },
      {
        "label": "Density",
        "benchmark": "density",
        "scope": "material"
      },
      {
        "label": "Latent heat of fusion",
        "benchmark": "latent_heat_of_fusion",
        "scope": "material"
      }
    ],
    "handling": [
      "Do not induce vomiting after swallowing: PubChem's first-aid text says so, and the aspiration hazard (H304) is the main concern.",
      "Keep it away from ignition sources. It is combustible, with a flash point of 135 °C closed cup on PubChem and 136 °C on Wikipedia.",
      "Check the supplier's safety data sheet for your grade, since PubChem's hazard data come from company notifications."
    ],
    "good_for": [
      "Passive buffering near 18 °C, as flown on IceCube: the instrument stayed near 18 °C most of the time in orbit (NASA).",
      "A melting point of 18.18 °C on PubChem, from the CRC Handbook."
    ],
    "watch_out": [
      "Aspiration hazard: PubChem's ECHA-based summary gives H304 for 96.9% of notifications.",
      "Flammable: PubChem lists both Flammable and Combustible, from NTP (1992).",
      "Sources disagree on the flash point (135 °C on PubChem, 136 °C on Wikipedia) and on skin irritation.",
      "The NASA paper says the paraffin mass was not adequate for the in-flight operation scheme, so the mass must match the scheme.",
      "No thermal conductivity, cycling or outgassing data for this grade were found in the sources read."
    ],
    "verdict": "n-Hexadecane is a paraffin phase change material with a melting point of 18.18 °C. It held an IceCube instrument near 18 °C in low Earth orbit, according to NASA. Its aspiration hazard (H304), combustibility and missing ageing data are the limits, so the PCM mass must be sized to the operation scheme.",
    "recipe": {
      "line": "n-Hexadecane is the unbranched saturated alkane C16H34, with sixteen carbons in a straight chain (Wikipedia). The sources read do not describe how it is made; the paraffin feedstock is slack wax from petroleum refining (see supply).",
      "parts": [
        {
          "name": "Carbon",
          "symbol": "C",
          "role": "Sixteen carbons form the straight chain.",
          "share_note": "standard atomic weight interval, see NIST",
          "source": "nist-atomic-weights",
          "where": "C row"
        },
        {
          "name": "Hydrogen",
          "symbol": "H",
          "role": "Thirty-four hydrogens complete the chain.",
          "share_note": "standard atomic weight interval, see NIST",
          "source": "nist-atomic-weights",
          "where": "H row"
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "PubChem's hazard data for hexadecane include an aspiration hazard from company notifications.",
        "points": [
          {
            "label": "Classification",
            "line": "The ECHA-based summary on PubChem gives H304 for 96.9% of notifications: May be fatal if swallowed and enters airways. The signal word is Danger."
          },
          {
            "label": "Skin",
            "line": "PubChem quotes one source calling it a severe human skin irritant and another calling it a mild eye and skin irritant."
          }
        ],
        "level": 2,
        "verdict": "Aspiration hazard (H304) in notifications"
      },
      {
        "title": "If it fails",
        "lead": "The failure routes in these sources are a PCM mass too small for the operation scheme, and fire.",
        "points": [
          {
            "label": "Mass",
            "line": "NASA states the paraffin mass was not adequate for the Day-On/Night-Off operation scheme flown on IceCube."
          },
          {
            "label": "Fire",
            "line": "PubChem lists it as flammable and combustible (NTP, 1992), with an NFPA 704 fire rating of 1."
          },
          {
            "label": "Decomposition",
            "line": "Heated to decomposition, it gives off acrid smoke and irritating vapors (Sax, quoted by PubChem)."
          }
        ],
        "level": 2
      },
      {
        "title": "Storage",
        "points": [
          {
            "label": "Stability",
            "line": "A Sigma-Aldrich safety data sheet, as quoted on PubChem, states: Stable under recommended storage conditions."
          }
        ]
      }
    ]
  },
  "updated": "2026-11-01",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 17,
    "unreachable": 6,
    "caveats": 2,
    "note": "Values were read by an AI assistant on 2026-11-01 from the pages named in each entry. The NASA paper was read from its PDF. The PubChem values come from its rendered page text. The flash point differs between PubChem (closed cup) and Wikipedia; both are recorded."
  },
  "sources": {
    "nist-webbook": {
      "title": "NIST Chemistry WebBook: hexadecane, phase change data",
      "id": "CAS 544-76-3; NIST Standard Reference Database 69",
      "url": "https://webbook.nist.gov/cgi/cbook.cgi?Mask=4&ID=C544763",
      "kind": "database",
      "license": "US government data"
    },
    "nist-webbook-cp": {
      "title": "NIST Chemistry WebBook: hexadecane, condensed phase thermochemistry (constant-pressure heat capacity of liquid)",
      "id": "CAS 544-76-3; NIST Standard Reference Database 69",
      "url": "https://webbook.nist.gov/cgi/cbook.cgi?ID=C544763&Units=SI&Mask=2",
      "kind": "database",
      "license": "US government data"
    },
    "nist-atomic-weights": {
      "title": "NIST Atomic Weights and Isotopic Compositions for All Elements (C and H rows)",
      "id": "C and H standard atomic weight intervals; H page https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=H&all=all&ascii=html",
      "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=C&all=all&ascii=html",
      "kind": "database",
      "license": "US government data"
    },
    "wikipedia-hexadecane": {
      "title": "Hexadecane, Wikipedia",
      "id": "Hexadecane article, lead and infobox",
      "url": "https://en.wikipedia.org/wiki/Hexadecane",
      "kind": "web",
      "license": "CC BY-SA 4.0, linked not reproduced"
    },
    "wikipedia-paraffin-wax": {
      "title": "Paraffin wax, Wikipedia",
      "id": "Paraffin wax article, sourcing and refining section",
      "url": "https://en.wikipedia.org/wiki/Paraffin_wax",
      "kind": "web",
      "license": "CC BY-SA 4.0, linked not reproduced"
    },
    "wikipedia-phase-change-material": {
      "title": "Phase-change material, Wikipedia",
      "id": "Phase-change material article, definition and organic PCM discussion",
      "url": "https://en.wikipedia.org/wiki/Phase-change_material",
      "kind": "web",
      "license": "CC BY-SA 4.0, linked not reproduced"
    },
    "wikipedia-cetane-number": {
      "title": "Cetane number, Wikipedia",
      "id": "Article text: hexadecane (also named n-hexadecane) is assigned a cetane number of 100",
      "url": "https://en.wikipedia.org/wiki/Cetane_number",
      "kind": "web",
      "license": "CC BY-SA 4.0, linked not reproduced"
    },
    "nasa-ntrs-pcm": {
      "title": "Thermal Assessment of Paraffin Phase Change Material Mini-Packs on IceCube 3U CubeSat in Flight",
      "id": "Choi, AIAA Propulsion and Energy Forum 2018, GSFC-E-DAA-TN54685, NTRS 20180004470",
      "url": "https://ntrs.nasa.gov/citations/20180004470",
      "year": 2018,
      "kind": "paper",
      "license": "NASA public document"
    },
    "pubchem-hexadecane": {
      "title": "PubChem compound record, Hexadecane (CID 11006)",
      "id": "CID 11006; CAS 544-76-3",
      "url": "https://pubchem.ncbi.nlm.nih.gov/compound/Hexadecane",
      "kind": "database",
      "license": "public domain (NCBI)"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/n-hexadecane-pcm/"
}