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Gas Encyclopedia

The Air Liquide Gas Encyclopedia ensures that you can quickly find full information on more than 135 gas molecules.

Air Liquide and its research teams are making reference content on gases available to students, scientists, professional users, and everyone interested.

Thanks to the Air Liquide Gas Encyclopedia, you will be able to:

  • Find all of the physical properties of gases (the main physical characteristics of molecules in their solid, liquid and gaseous or supercritical states),
  • Calculate the correspondence between the gaseous and liquid phase for a given weight or volume of gas,
  • Calculate the liquid phase density all along the liquid-vapor balance curve for nitrogen, carbon dioxide, argon, hydrogen or oxygen,
  • Download the vapor pressure curve for some gases,
  • View the Safety Datasheets (SDS),
  • Discover the main applications of these gases in industry and healthcare,
  • Check material compatibility.

Using the Encyclopedia

You can run a search by entering a chemical formula, a UN transportation code or by choosing a molecule name from the drop-down menu. Having trouble? Refer to our User Guide.
Gas selection
After selecting a molecule, you can choose the units in which you want displayed numeric values.
Nitrogen dioxide
Nitrogen dioxide
CAS Number : 10102-44-0

;Nitrogen peroxide;
Main applications
  • Industries

  • Nitrogen dioxide is a strong nitrating or oxidizing agent in organic synthesis.
  • Nitric dioxide is used in calibration gas mixtures for petrochemical industry; environmental emission monitoring, industrial hygiene monitors and trace impurity analyzers.
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Gas Properties
Molecular Weight
  • Molecular weight  : 46.006 g/mol
Solid phase
  • Melting point  : -11.2 °C
  • Latent heat of fusion (1,013 bar, at melting point) : 318.437 kJ/kg
Liquid phase
  • Liquid density (1.013 bar at boiling point) : 1447.58 kg/m3
  • Liquid/gas equivalent (1.013 bar and 25 °C (77 °F)) : 424 vol/vol
  • Boiling point (1.013 bar) : 21 °C
  • Latent heat of vaporization (1.013 bar at boiling point) : 828.51 kJ/kg
  • Vapor pressure (at 20 °C or 68 °F) : 1 bar
Critical point
  • Critical temperature  : 158 °C
  • Critical pressure  : 101.32 bar
  • Critical density  : 557.717 kg/m3
Triple point
  • Triple point temperature  : -11.25 °C
  • Triple point pressure  : 0.187 bar
Gaseous phase
  • Gas density (1.013 bar at boiling point) : 3.4 kg/m3
  • Compressibility Factor (Z) (1.013 bar and 15 °C (59 °F)) : 0.992
  • Specific gravity  : 2.62
  • Specific volume (1.013 bar and 25 °C (77 °F)) : 0.512 m3/kg
  • Heat capacity at constant pressure (Cp) (1.013 bar and 24.3 °C (76 °F)) : 3.699657E-02 kJ/(mol.K)
  • Viscosity (1.013 bar and 25 °C (77 °F)) : 1.3311E-09 Poise
  • Thermal conductivity (1.013 bar and 25 °C (77 °F)) : 12.961 mW/(m.K)
Go back to choosing the units
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Vapor Pressure Graph
Vapor Pressure Graph
The vapor pressure curve may be obtained by clicking on the image. On the graph, pressure is in bar or 0.1 MPa, temperature in K or °C. The critical point is indicated by a black spot on the liquid-vapor equilibrium curve.

Safety Data Sheets
Safety Data Sheets (SDS) include information on product ingredients, physical and chemical properties, potential effects on toxicology and ecology, identification of hazards, handling and storage instructions, as well as personnel protection recommendations and information related to transportation requirements, first-aid and emergency processes.


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Major Hazards
  • Major hazard : Inhalation and Reactivity
  • Toxicity (Am. Conf. Of Gov. Ind. Hygienists ACGIH 2000 Edition) : 3 ppm
  • Flammability limits in air (STP conditions) : Highly Oxidising
  • Odour : Slightly Irritating
  • UN Number : UN1067
  • DOT Label (USA) : PG & FG
  • DOT Hazard class (USA) : Poison A
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Material compatibility
Air Liquide has assembled data on the compatibility of gases with materials to assist you in evaluating which products to use for a gas system. Although the information has been compiled from what Air Liquide believes are reliable sources (International Standards: Compatibility of cylinder and valve materials with gas content; Part 1: ISO 11114-1 (Jul 1998), Part 2: ISO 11114-2 (Mar 2001)), it must be used with extreme caution. No raw data such as this can cover all conditions of concentration, temperature, humidity, impurities and aeration. It is therefore recommended that this table is used to choose possible materials and then more extensive investigation and testing is carried out under the specific conditions of use. The collected data mainly concern high pressure applications at ambiant temperature and the safety aspect of material compatibity rather than the quality aspect.
General Behavior : Corrosive in presence of water.
  • Aluminium
    Satisfactory but corrosive in presence of moisture.
  • Brass
    Non recommended
  • Copper
    Non recommended
  • Ferritic Steels (e.g. Carbon steels)
    Satisfactory but corrosive in presence of water.
  • Stainless Steel
    Satisfactory but corrosive in presence of water except for hight quality stainless steel.
  • Polytetrafluoroethylene (PTFE)
  • Polychlorotrifluoroethylene (PCTFE)
  • Vinylidene polyfluoride (PVDF) (KYNAR)
    Non recommended, possible ignition.
  • Polyamide (PA) (NYLON)
    Non recommended, possible ignition.
  • Polypropylene (PP)
    Non recommended, possible ignition.
  • Buthyl (isobutene - isoprene) rubber (IIR)
    Non recommended, possible ignition.
  • Nitrile rubber (NBR)
    Non recommended, possible ignition.
  • Chloroprene (CR)
    Non recommended, possible ignition.
  • Chlorofluorocarbons (FKM) (VITON)
    Non recommended, possible ignition.
  • Silicon (Q)
    Non recommended, possible ignition.
  • Ethylene - Propylene (EPDM)
    Non recommended, possible ignition.
  • Hydrocarbon based lubricant
    Non recommended, possible ignition and contamination of the material.
  • Fluorocarbon based lubricant
    Non recommended, contamination of the material by the gas.
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Selection of the units
You can choose the units in which the values are displayed. By default, SI units are selected.


  • Quantity


  • Mass
    kg lb g
  • Volume
    m3 ft3 l
  • Pressure
    bar psi kPa
  • Temperature
    °C °F K °R
  • Density
    kg/m3 lb/ft3 mol/l (lb-mol)/ft3
  • Enthalpy
    kJ/kg Btu/lb kJ/mol kcal/kg kcal/mol Btu/lb-mol
  • Heat Capacity
    kJ/(mol.K) Btu/(lb.°F) kJ/(kg.K) Btu/(lb-mol.°F) kcal/(kg.K)
    cal/(mol.K) J/(mol.K)
  • Viscosity
    Poise lb/(ft.s) µPa.s Pa.s
  • Thermal Conductivity
    mW/(m.K) Btu.ft/(h.ft2.°F) cal.cm/(h.cm2.°C) W/(m.K)
  • Concentration
    vol % vol ppm vol/vol
  • Solubility
    vol/vol lb/ft3 (lb-mol)/ft3 mol/l g/l
  • Specific volume
    m3/kg ft3/lb l/mol ft3/lb-mol

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