PHYSICAL PROPERTIES
| Molecular weight | 4,0038 |
| Colour | none |
| Odour | none |
| Boiling temperature | -268,9oC |
| Triple point temperature | -271,3oC |
| Density of helium gas (at atm. pressure 0,101 Mpa) | 0,165 kg/m3 |
RESERVES / PRODUCTION
Athough helium is the second most abundant element in the Universe, it's reserves on Earth are very limited and non-renewable.
Helium is extracted from natural gas of average content 0,1%-0,5%. Most of the natural gas reserves being sources of helium are located in the USA (Midcontinent and Rocky Mountain Region). Helium produced outside the United States is extracted in Algeria, Qatar, Russia and Poland.
Helium mostly is extracted by low-temperature distillation, in which crude helium is finally purified through low-temperature condensation and with the use of activated charcoal.
Another method to recover and purify helium is diffusion of natural gas through membranes.