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      Hydrogen
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      Hydrogen
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      H2
      Hydrogen

      Physical Properties

      Under solid (grey), liquid (blue) and vapor states (white) along the equilibrium curves

      • General properties
      • Solid phase
      • Liquid Phase
      • Gas Phase
      (P)
      log(P)
      Download
      • Molecular weight
        2.016
        g/mol
      • Content in dry air
        /

      Critical Point

      • Temperature
        - 239.96
        °C
         - 399.928 °F 33.19 K
      • Pressure
        13.13
        bar
         1.313E6 pa 190.4345 lbf/in2 12.9583 Atm 1313 Kpa 9848.3371 mmHg
      • Density
        31.43
        kg/m³
         1.9621 lb/ft³

      Triple Point

      • Temperature
        - 259.19
        °C
         - 434.542 °F 13.96 K
      • Pressure
        7.7E-2
        bar
         7700 pa 1.1168 lbf/in2 7.5993E-2 Atm 7.7 Kpa 57.7549 mmHg
      Pressure 1.013 bar
      • Melting point
        - 259.2
        °C
         - 434.56 °F 13.95 K
      • Latent heat of fusion (at melting point)
        58.089
        kJ/kg
         24.9905 Btu/lb 13.8836 kcal/kg
      • Solid density
        /
      Pressure 1.013 bar
      • Liquid density (at boiling point)
        70.516
        kg/m³
         4.4022 lb/ft³
      • Boiling point
        - 252.78
        °C
         - 423.004 °F 20.37 K
      • Latent heat of vaporization (at boiling point)
        448.69
        kJ/kg
         193.0314 Btu/lb 107.2395 kcal/kg
      Pressure1.013barTemperature
      • Compressibility factor Z
        1.0006
        1.0006
        1.0006
      • Cp/Cv ratio γ
        1.4098
        1.4069
        1.4054
      • Dynamic viscosity
        8.3969E-5
        Po
         8.3969 µPa.s 8.3969E-6 PA.S 5.6425E-6 lb/ft/s
        8.7098E-5
        Po
         8.7098 µPa.s 8.7098E-6 PA.S 5.8527E-6 lb/ft/s
        8.9154E-5
        Po
         8.9154 µPa.s 8.9154E-6 PA.S 5.9909E-6 lb/ft/s
      • Gas density at boiling point
        1.438
        kg/m³
         8.9771E-2 lb/ft³
        1.438
        kg/m³
         8.9771E-2 lb/ft³
        1.438
        kg/m³
         8.9771E-2 lb/ft³
      • Gas density
        8.99E-2
        kg/m³
         5.6123E-3 lb/ft³
        8.52E-2
        kg/m³
         5.3189E-3 lb/ft³
        8.23E-2
        kg/m³
         5.1378E-3 lb/ft³
      • Heat capacity at constant pressure Cp
        14.1976
        kJ/(kg.K)
         3.3933 BTU/lb∙°F 1.4198E4 J/kg∙K 3.3933 kcal/kg∙K
        14.2676
        kJ/(kg.K)
         3.41 BTU/lb∙°F 1.4268E4 J/kg∙K 3.41 kcal/kg∙K
        14.3063
        kJ/(kg.K)
         3.4193 BTU/lb∙°F 1.4306E4 J/kg∙K 3.4193 kcal/kg∙K
      • Heat capacity at constant volume Cv
        10.0704
        kJ/(kg.K)
         2.4069 BTU/lb∙°F 1.007E4 J/kg∙K 2.4069 kcal/kg∙K
        10.1409
        kJ/(kg.K)
         2.4237 BTU/lb∙°F 1.0141E4 J/kg∙K 2.4237 kcal/kg∙K
        10.1796
        kJ/(kg.K)
         2.433 BTU/lb∙°F 1.018E4 J/kg∙K 2.433 kcal/kg∙K
      • Liquid (at boiling point)/gas equivalent
        785.24
        mol/mol
        831.17
        mol/mol
        857.09
        mol/mol
      • Solubility in water
        /
        1.51E-5
        mol/mol
        1.411E-5
        mol/mol
      • Specific gravity
        0.07
        0.07
        0.07
      • Specific volume
        11.128
        m³/kg
         178.2533 ft³/lb
        11.739
        m³/kg
         188.0406 ft³/lb
        11.983
        m³/kg
         191.9491 ft³/lb
      • Thermal conductivity
        172.58
        mW/m∙K
         9.9781E-2 Btu/ft/h/°F 1.4849 cal/hour∙cm∙°C 4.1248E-4 cal/s∙cm∙°C 1.7258E-1 W/(m∙K)
        180.05
        mW/m∙K
         1.041E-1 Btu/ft/h/°F 1.5492 cal/hour∙cm∙°C 4.3033E-4 cal/s∙cm∙°C 1.8005E-1 W/(m∙K)
        184.88
        mW/m∙K
         1.0689E-1 Btu/ft/h/°F 1.5907 cal/hour∙cm∙°C 4.4187E-4 cal/s∙cm∙°C 1.8488E-1 W/(m∙K)
      • Vapor pressure
        /
        /
        /
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      H2
      Hydrogen

      Liquid / Gas Volumes

      Calculate a liquid or gas volume or a mass

      Liquid Phase

      At boiling point at 1.013 bar

      m3(Volume)
      kg(Mass)

      Gas Phase

      at 1.013 bar and boiling point

      m3(Volume)
      kg(Mass)
      Retour
      H2
      Hydrogen

      Applications

      Examples of uses of this molecule in Industry and Healthcare

      Aeronautics

      Aviation companies are currently testing and examining the potential for using hydrogen to replace the Auxiliary Power Units (APUs) and use fuel cells to generate electrical power for non-essential aircraft applications.

      Aeronautics

      Space

      Liquid hydrogen is used as rocket or launcher propellant. In combination with an oxidizer such as liquid oxygen, liquid hydrogen yields the highest specific impulse, or efficiency in relation to the amount of propellant consumed of any known rocket propellant.

      Space

      Automotive

      Hydrogen is also a carbon-free fuel to electric vehicles. An on-board hydrogen tank and fuel cell are used to respectively store the hydrogen and produce electricity for the car vehicle. Hundreds of hydrogen forklifts, cars and buses are already in service. Hydrogen is used for metal heat treatment in vehicles. It is also used in mixtures for arc and plasma welding of stainless steels.

      Automotive

      Chemicals

      Hydrogen is used for the synthesis of amines (e.g. aniline) or alkanes from alkenes (e.g. cyclohexane) via hydrogenation reactions. Hydrogen is used for methanol production from synthesis gas, a mixture of hydrogen and carbon monoxide. It is an important starting point to produce valuable products such as dimethyl ether (DME) and propylene that are important sources of industrial chemicals and plastic products.

      Chemicals

      Electronic components

      Hydrogen is a carrier gas in semiconductor processes, especially for silicon deposition and crystal growing. It is also a scavenger gas in atmosphere soldering as well as for annealing of copper films. Hydrogen allows a complete elimination of oxygen and its inconveniences in medium to high temperature processes when used as forming gas (hydrogen diluted in nitrogen). Hydrogen provides a reducing atmosphere while mixing reactive molecules.

      Electronic components

      Food

      Hydrogen is used for the hydrogenation of amines and fatty acids for food solid fats production.

      Food

      Glass

      Hydrogen mixed with nitrogen creates a reductive atmosphere over the tin bath in glass production process preventing oxygen to react with the tin. Hydrogen is used in heat treatment (oxy-hydrogen flame) of hollow glass and optic fibers pre-forms.

      Glass

      Laboratories & Research Centers

      Hydrogen is a carrier gas in gas chromatography and in various analytical instrument applications. It helps move the substance to analyse through the process.

      Laboratories & Research Centers

      Metal

      Hydrogen, mixed with protective inert gases (H2 diluted in nitrogen) eliminates all oxygen traces, harmful for these medium and high temperature processes. Hydrogen, mixed with nitrogen, is used for metal heat treatment. Heat treatment is a sequence of heating operations applied to metals - sheets, tubes, wires or parts - to improve their mechanical properties, by modifying their structure or composition. Hydrogen is also used in mixtures for arc or plasma welding of stainless steels.

      Metal

      Oil & Gas

      Hydrogen is used in refinery to remove sulfur from petroleum products (hydrodesulfurization process), thus reduce sulfur dioxide emissions during fuel combustion and prevent acid rain. Hydrogen is used in many other units in refineries : to crack long-chain hydrocarbons into lighter hydrocarbons (hydrocracking process), to convert normal paraffins into iso-paraffins and improve the product properties (hydroisomerisation) and to remove aromatic compounds from a mixture, especially as part of the oil refining process (dearomatisation).

      Oil & Gas

      Other

      Hydrogen fuel cells can be used as clean and autonomous power supply for off-grid sites, such as telecommunication stations and to power residential homes.

      Photonics

      Hydrogen is used in the fabrication of fibre optic as a high purity gas.

      Photonics
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      H2
      Hydrogen

      Safety & Compatibility

      Information to safely use this molecule

      • Major hazards
      • Material compatibility
      Safety
      • GHS02
        Flammable
      • GHS04
        Gas under pressure

      Autoignition Temperature in Air at Patm and Flammability Limits in Air at Patm and 293.15 K (except if the temperature is indicated)

      • Europe (according to EN1839 for Limits and EN 14522 for autoignition temperature)

        • Auto-ignition temperature
          560
          °C
           1040 °F 833.15 K
        • Flash point
          /
        • Lower flammability limit
          /
        • Upper flammability limit
          /

      • US (according to NFPA for Limits and ASTM E659 for autoignition temperature)

        • Auto-ignition temperature
          500
          °C
           932 °F 773.15 K
        • Flash point
          /
        • Lower flammability limit
          /
        • Upper flammability limit
          /

      Odor

      none

      Metals

      • Aluminium
        Satisfactory
      • Brass
        Satisfactory
      • Monel
        Satisfactory
      • Copper
        Satisfactory
      • Ferritic Steel
        Satisfactory
        risk of embrittlement
      • Stainless steel
        Satisfactory
        risk of embrittlement
      • Zinc
        Satisfactory
      • Titanium
        Satisfactory
        risk of embrittlement

      Plastics

      • Polytetrafluoroethylene
        Acceptable
        strong rate of permeation
      • Polychlorotrifluoroethylene
        Satisfactory
      • Polyvinylidene fluoride
        Satisfactory
      • Polyvinyl chloride
        Satisfactory
      • Ethylene tetrafluoroethylene
        Satisfactory
      • Polycarbonate
        Satisfactory
      • Polyamide
        Satisfactory
      • Polypropylene
        Acceptable
        strong rate of permeation

      Elastomers

      • Buthyl (isobutene- isoprene) rubber
        Satisfactory
      • Nitrile rubber NBR
        Satisfactory
      • Chloroprene
        Satisfactory
      • Silicon
        Acceptable
        strong rate of permeation
      • Perfluoroelastomers
        Satisfactory
      • Fluoroelastomers
        Satisfactory
      • Neoprene
        Satisfactory
      • Polyurethane
        Satisfactory
      • Ethylene-Propylene
        Satisfactory
      • Satisfactory

      Lubricants

      • Hydrocarbon based lubricant
        Satisfactory
      • Fluorocarbon based lubricant
        Satisfactory

      Materials compatibility

      Recommendations : Air Liquide has gathered data on the compatibility of gases with materials to assist you in evaluating which materials 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- Metallic materials: ISO11114-1 (March 2012), Part 2 - Non-metallic materials: ISO11114-2 (April 2013), it must be used with extreme caution and engineering judgement. No raw data such as these can cover all conditions of concentration, temperature, humidity, impurities and aeration. It is therefore recommended that this table is only used to identify possible materials for applications at high pressure and ambient temperature. Extensive investigation and testing under the specific conditions of use need to be carried out to validate a material selection for a given application. Contact the regional Air Liquide team for expertise service.

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      H2
      Hydrogen

      Learn More

      General information

      More information

      Hydrogen was discovered by Henry Cavendish in 1766. It owes its name to Antoine Laurent de Lavoisier, who combined the Greek "hydor", "water", and "genen", "to engender". Hydrogen is colorless, very light, and reacts easily with other chemical substances making it a very useful reactant for the chemical and oil industries. Hydrogen is found in the atmosphere at trace levels. In 1970, hydrogen fluxes have been detected in the oceans, resulting from serpentinization of rocks but the exploitation seems unlikely due to extreme geological conditions. More recently, natural hydrogen emissions from the ground have also been detected and are under investigation to understand the origin of this hydrogen. Today natural gas or hydrocarbons as well as water are used as raw materials to produce hydrogen. Moreover, hydrogen has a very high energy content (120 MJ/kg) while containing no carbon atom. This makes it a promising energy vector for the future. Associated to air or oxygen in a fuel cell, hydrogen is converted in electricity and heat, releasing only water. Driving an electric car over a long distance with no emission is a dream of many !

      H2

      Hydrogen