| 4He | 3He | N2 | H2 | O2 | ||
|---|---|---|---|---|---|---|
| Molar mass | g/mol | 4.003 | 3 | 28.013 | 2.016 | 16 |
| Boiling temperature | K | 4.21 | 3.19 | 77.4 | 20.3 | 90.2 |
| Density (fluid) | g/l | 125.0 | ? | 808.6 | 70.8 | ? |
| Density (gas) | g/l | 16.89 | ? | 4.59 | 13.38 | ? |
| Latent heat | J/g | 20.6 | ? | 198.6 | 445.5 | ? |
| Latent heat | kJ/l | 2.56 | 0.48 | 160.6 | 31.5 | 245 |
| Critical temperature | K | 5.20 | 3.32 | 126.0 | 33.0 | 154.3 |
| Critical pressure | bar | 2.28 | 1.16 | 33.9 | 13.0 | 50.4 |
| Triple temperature | K | - | - | 63.15 | 13.8 | 54.36 |
| Triple pressure | mbar | - | - | 125.3 | 70.4 | 15 |
The picture below shows the vapor pressure of 4He. According to the International Temperature Scale of 1990 (ITS-90) the temperature between 1.25 K and 5.0 K is defined by this vapor pressure, and the pressure curve for this temperature range is described by an analytical expression (the formula is part of ITS-90).
Vapor Pressure Curve of 4He