Color: colorless
State at 25°C: gas
Density (g/cm3): 0.0002
Hardness (Mohs): No data 
Melting Point (K): No data
Boiling Point (K): 4.2
Heat of Fusion (kJ/mol): No data
Heat of Vaporization (kJ/mol): 0.1
Heat of Atomization (kJ/mol): 0
Therm. Conductivity (J/m sec K): 0.15
Elec. Conductivity (1/mohm cm): No data
Abundance, Solar System: 9.435
Abundance, Earth's Crust: -2.1
Pure Cost ($/100g): $ 5.20
Bulk Cost ($/100g):  
Source: Natural gas, air