Helium, He
Molecular weight g/mol: 4.003
Purity: 99.9999%
CAS: 7440-59-7 EC: 231-168-5 UN: 1046 (Compressed); 1963 (Refrigerated liquid)
Typical Filling Pressure: 15 °C: 200 bar(a) 70 °F: 2,640 psi(g)
Characteristics: Colourless and odourless gas. Non-reactive. Asphyxiant in high concentrations.
| Liquid State | |
| Density at b.p. 1 atm kg/l: | 0.1240 |
| Density 20 °C kg/l: | |
| Vapor pressure 20 °C bar: | |
| Specific heat kJ/kg*K: | |
| Rel.Spec.wgt, air=1 (15 °C.1 bar): | 0.14 |
| Density 15 °C 1 atm kg/m3: | 0.17 |
| Gaseous state | |
| Specific heat (15 °C) kJ/kg* K: | 5.193 |
| Thermal conductivity µW/cm• K: | |
| Solubility in water at P=1 bar l/kg: | |
| Boiling point (1 atm) | |
| Temp. °C: | -268.9 |
| Heat of vaporization kJ/kg | 20.8 |
| Critical point | |
| Temp. °C: | -268.0 |
| Pressure bar: | 2.28 |
| Density kg/l: | 0.0699 |
| Flammability in air | |
| Lower limit % volume: | n.a. |
| Upper limit % volume: | n.a. |