Table 3: The most important properties of gases used in the permeability experiments.


Molecular diameter/cm·10−83.153.342.98
Mean free path/cm·10−
Average velocity/cm s−1·10−2471376440
Van der Waals constant a/bar L2 mol−21.393.591.36
Van der Waals constant b/L mol·10−23.914.273.18
Molar mass/kg kmol−128.01344.0131.999
Critical volume/cm3 mol−190.19478
Viscosity/ P176147204
Gas density/kg m−31.251.981.43
Molecular volume/cm3 mol−131.230.725.6
Solubilities of gases in water at different temperatures/cm3 dm−316.0 (20°C)
12.5 (40°C)
10.2 (60°C)
878 (20°C)
530 (40°C)
360 (60°C)
31 (20°C)
23 (40°C)
19 (60°C)
Diffusion coefficients of gases in water at 20°C/cm2 s−1·1051.641.771.8
Kinetic diameter/cm 10−83.643.303.46
Critical temperature/K126.2304.2154.8
Critical pressure/MPa3.397.395.08
Gas constant/kJ kg−1 K−10.29680.18890.2598
Effective diameter/cm 10−8 3.663.633.44
Collision diameter/cm  3.684.003.43
Lennard-Jones force constant91.5190113