Liquid hydrogen

Liquid hydrogen (H2(l)) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form.[4]

Liquid hydrogen
IUPAC name
Systematic IUPAC name
Liquid hydrogen
Other names
Hydrogen (cryogenic liquid), Refrigerated hydrogen; LH2, para-hydrogen
3D model (JSmol)
RTECS number
  • MW8900000
UN number 1966
  • InChI=1S/H2/h1H checkY
  • InChI=1/H2/h1H
  • [H][H]
Molar mass 2.016 g·mol−1
Appearance Colorless liquid
Density 70.85 g/L (4.423 lb/cu ft)[1]
Melting point −259.14 °C (−434.45 °F; 14.01 K)[2]
Boiling point −252.87 °C (−423.17 °F; 20.28 K)[2]
GHS labelling:[3]
GHS02: FlammableGHS04: Compressed Gas
H220, H280
P210, P377, P381, P403
NFPA 704 (fire diamond)
571 °C (1,060 °F; 844 K)[2]
Explosive limits LEL 4.0%; UEL 74.2% (in air)[2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

To exist as a liquid, H2 must be cooled below its critical point of 33 K. However, for it to be in a fully liquid state at atmospheric pressure, H2 needs to be cooled to 20.28 K (−252.87 °C; −423.17 °F).[5] A common method of obtaining liquid hydrogen involves a compressor resembling a jet engine in both appearance and principle. Liquid hydrogen is typically used as a concentrated form of hydrogen storage. Storing it as liquid takes less space than storing it as a gas at normal temperature and pressure. However, the liquid density is very low compared to other common fuels. Once liquefied, it can be maintained as a liquid in thermally insulated containers.[6]

There are two spin isomers of hydrogen; liquid hydrogen consists of 99.79% parahydrogen and 0.21% orthohydrogen.[5]

Share this article:

This article uses material from the Wikipedia article Liquid hydrogen, and is written by contributors. Text is available under a CC BY-SA 4.0 International License; additional terms may apply. Images, videos and audio are available under their respective licenses.