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Substance Name: Helium [USP]
RN: 7440-59-7
UNII: 206GF3GB41


  • A noble gas with the atomic symbol He, atomic number 2, and atomic weight 4.003. It is a colorless, odorless, tasteless gas that is not combustible and does not support combustion. It was first detected in the sun and is now obtained from natural gas. Medically it is used as a diluent for other gases, being especially useful with oxygen in the treatment of certain cases of respiratory obstruction, and as a vehicle for general anesthetics.

Molecular Formula

  • He

Molecular Weight

  • 4.0026

Classification Codes

Classification Code

  • Gases, Diluent for

Superlist Classification Code

  • Simple Asphyxiant
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Names and Synonyms

Name of Substance

  • Helium
  • Helium [USP]

MeSH Heading

  • Helium


  • Atomic helium
  • EINECS 231-168-5
  • Helium
  • Helium-4
  • HSDB 553
  • o-Helium
  • p-Helium
  • UNII-206GF3GB41

Systematic Name

  • Helium

Superlist Names

  • Helium
  • Helium, compressed
  • Helium, compressed [UN1046] [Nonflammable gas]
  • Helium, refrigerated liquid (cryogenic liquid)
  • Helium, refrigerated liquid (cryogenic liquid) [UN1963] [Nonflammable gas]
  • UN1046
  • UN1963

Registry Numbers

CAS Registry Number

  • 7440-59-7


  • 206GF3GB41

Other Registry Numbers

  • 1312815-28-3
  • 494798-31-1

System Generated Number

  • 0007440597

Structure Descriptors







Physical Properties

Physical Property Value Units Temp (deg C) Source
Melting Point -2.68E+02 deg C   EXP
Boiling Point -2.69E+02 deg C   EXP
log P (octanol-water) 0.28 (none)   EXP
Water Solubility 2.5 mg/L 21 EXP
Atmospheric OH Rate Constant 0.0 cm3/molecule-sec 25 EST

Physical property data is provided to ChemIDplus by SRC, Inc.