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Hydrogen (H2) Properties, Uses, Applications
Hydrogen Gas and Liquid Hydrogen

Interesting Facts Physical Properties Applications & Uses
Interesting Facts and Information about Hydrogen (H2):

Hydrogen (H2) is a colorless, odorless, tasteless, flammable and nontoxic gas at atmospheric temperatures and pressures. It is the most abundant element in the universe, but is almost absent from the atmosphere as individual molecules in the upper atmosphere can gain high velocities during collisions with heavier molecules, and become ejected from the atmosphere. It is still quite abundant on Earth, but as part of compounds such as water.  

Hydrogen burns in air with a pale blue, almost invisible flame. Hydrogen is the lightest of all gases, approximately one-fifteenth as heavy as air.  Hydrogen ignites easily and forms, together with oxygen or air, an explosive gas (oxy-hydrogen).

Hydrogen has the highest combustion energy release per unit of weight of any commonly occurring material. This property makes it the fuel of choice for upper stages of multi-stage rockets. 

Hydrogen has the lowest boiling point of any element except helium.  When cooled to its boiling point, -252.76o C (-422.93o F) hydrogen becomes a transparent, odorless liquid that is only one-fourteenth as heavy as water. Liquid hydrogen is not corrosive or particularly reactive. When converted from liquid to gas, hydrogen expands approximately 840 times. Its low boiling point and low density result in liquid hydrogen spills dispersing rapidly.

The most common large-scale process for manufacturing hydrogen is steam reforming of hydrocarbons, in particular, natural gas (mostly methane). Other methods used for hydrogen production methods include generation by partial oxidation of coal or hydrocarbons, electrolysis of water, recovery of byproduct hydrogen from electrolytic cells used to produce chlorine and other products, and dissociation of ammonia. Hydrogen is recovered for internal use and sale from various refinery and chemical streams, typically purge gas, tail gas, fuel gas or other contaminated or low-valued streams. Purification methods include pressure swing adsorption (PSA), cryogenic separation and membrane gas separation. 

Many hydrogen gas users purchase it as a liquid, which can be vaporized as needed, instead of producing it on their own site.  Liquefaction of gaseous hydrogen is a multi-stage process using several refrigerants and compression/ expansion loops to produce extreme cold. As part of the process, the hydrogen passes through "ortho/ para" conversion catalyst beds that convert most of the "ortho" hydrogen to the "para" form.  These two types of diatomic hydrogen have different energy states. In "ortho" hydrogen, which is the most common form at room temperature, making up approximately 75% of the mixture, the nuclei have parallel proton spins. In "para" hydrogen the nuclei have anti-parallel proton spins. "Ortho" hydrogen is less stable than "para" at liquid hydrogen temperatures. The equilibrium mix is almost all para-hydrogen which means that over time, any liquefied ortho hydrogen will change to the "para" form.  This spontaneous change releases energy, and results in vaporizing a portion of the liquid in storage.  To minimize this, a catalytic conversion step is used to maximize the percentage of para hydrogen sent to storge.  A commonly used catalyst is hydrous ferric oxide.

Some industrial processes with relatively small hydrogen requirements may choose to produce some or all of their needs using compact generators.  In the past, ammonia dissociation was a common technology choice.  More recently, improvements in small packaged electrolytic and hydrocarbon reforming systems have made these routes to small volume hydrogen production increasingly attractive.  In some cases these packaged systems may be the sole source of hydrogen at a site, or they may be used to supplement and/or back-up other supply sources. 

Highly packaged, compact hydrocarbon reformer units have made it possible to utilize on-site hydrocarbon reforming at much lower production rates than were considered commercially feasible only a few years ago. Similarly, increasingly energy efficient electrolytic hydrogen production units, which use water and electric power to produce high purity hydrogen at common in-plant distribution pressures, are being applied at amenable hydrogen user sites. 

Much has been said about hydrogen being the "fuel of the future" due to its abundance and its non-polluting combustion products.  Less has been said about the fact that other forms of energy must be consumed to produce the hydrogen which will be used as fuel.  Most hydrogen is derived from compounds such as water or methane, and energy is required to break the hydrogen free from these compounds, then separate, purify, compress and/ or liquefy the hydrogen for storage and transportation to usage points. Widespread production, distribution and use of hydrogen will require many innovations and investments to be made in efficient and environmentally-acceptable production systems, transportation systems, storage systems and usage devices. 

Currently, there is a great deal of interest in hydrogen fuel cell technology development and investigations into unconventional or specialized hydrogen storage systems. New technologies and equipment developed to support these applications will undoubtedly find uses in industry as well.

English Units  NormalBoiling Point
(1 atm)
Gas Phase Properties
@ 32F & @1 atm
Liquid Phase Properties
@ B P& @ 1 atm
Triple Point Critical Point
Temp. Latent Heat of Vaporization Specific Gravity Specific Heat (Cp) Density Specific Gravity Specific Heat (Cp) Temp. Pressure Temp. Pressure Density
Substance Chemical
F BTU/lb Air = 1 BTU/lb F lb/cu. ft Water = 1 BTU/lb F F psia F psia lb/cu ft
Hydrogen H2 2.02 -423 191.7 0.06998 3.425 0.005611 0.071 2.309 -434.6 1.045 -399.93 190.8 1.88
 Metric Units   Boiling Point
@ 101.325 kPa
Gas Phase Properties
@ 0 C & @ 101.325 kPa
Liquid Phase Properties
@ B.P., & @ 101.325 kPa
Triple Point Critical Point
Temp. Latent Heat of Vaporization Specific Gravity Specific Heat (Cp) Density Specific Gravity Specific Heat (Cp) Temp. Pressure Temp. Pressure Density
Substance Chemical
C kJ/kg Air = 1 kJ/kg C kg/m3 Water = 1 kJ/kg C C kPa abs C kPa abs kg/m3
Hydrogen H2 2.02 -252.8 446.0 0.06998 14.34 0.08988 0.071 9.668 -259.2 7.205 -239.96 1315 30.12
Hydrogen (H2) Applications and Uses:

Hydrogen is mixed with inert gases to obtain a reducing atmosphere, which is required for many applications in the metallurgical industry, such as heat treating steel and welding.  It is often used in annealing stainless steel alloys, magnetic steel alloys, sintering and copper brazing.

Hydrogen can be produced by dissociation of ammonia at about 1800˚F with the aid of a catalyst - which results in a mix of 75% hydrogen and 25% mononuclear nitrogen (N rather than N2). The mix is used as a protective atmosphere for applications such as brazing or bright annealing.

Chemicals, Pharmaceuticals and Petroleum:

Hydrogen is used in large quantities as a raw material in the chemical synthesis of ammonia, methanol, hydrogen peroxide, polymers, and solvents. 

In refineries, it is used to remove the sulfur that contained in crude oil.  Hydrogen is catalytically combined with various intermediate processing streams and is used, in conjunction with catalytic cracking operations, to convert heavy and unsaturated compounds to lighter and more stable compounds.

The pharmaceutical industry uses hydrogen to manufacture vitamins and other pharmaceutical products.

Large quantities of hydrogen are used to purify gases (e.g. argon) that contain trace amounts of oxygen, using catalytic combination of the oxygen and hydrogen followed by removal of the resulting water. 

Glass and Ceramics:

In float glass manufacturing, hydrogen is required to prevent oxidation of the large tin bath. 

Food and Beverages:

It  is used to hydrogenate unsaturated fatty acids in animal and vegetable oils, producing solid fats for margarine and other food products. 


Hydrogen is used as a carrier gas for such active trace elements as arsine and phospine, in the manufacture of semi-conducting layers in integrated circuits.


Generators in large power plants are often cooled with hydrogen, since the gas processes high thermal conductivity and offers low friction resistance.

Liquid hydrogen is used as a rocket fuel.

The nuclear fuel industry uses hydrogen as a protective atmosphere in the fabrication of fuel rods.

Hydrogen Safety: Material Safety Data Sheets and related Information: Information on MSDS content and uses.  Links to UIG / UCG MSDS Library, to DOT Emergency Response Guidebook, to NFPA Hazard Ratings definitions.  
General Information:  Industrial Gases
Safety and  Emergency Response
MSDS  for
Gaseous Hydrogen

Properties, Applications and Uses of Other Industrial Gases:

Neon, Krypton, Xenon Oxygen Argon Carbon Dioxide Nitrogen

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