Low Pressure Properties of Air at 22°C

Pressure (Pa) n d M
1.01x105(760 Torr) 2.48x10+25 3.43x10-09 6.6x10-08
100(0.75 Torr) 2.45x10+22 3.44x10-08 6.6x10-05
1(7.5 Torr) 2.45x10+20 1.60x10-07 6.6x10-03
1x10-3(7.5x10-6 Torr) 2.45x10+17 1.60x10-06 6.64
1x10-5(7.5x10-8 Torr) 2.45x10+15 7.41x10-06 664
1x10-7(7.5x10-10 Torr) 2.45x10+13 3.44x10-05 66,000
n = Particle density.
d = average molecular spacing.
M = Mean Free Path (metre)

Defined Values and Conversion Factors

Atomic Mass Unit 1/12th the mass of an atom of the C12 nuclide
Standard acceleration of free fall 9.80665 m/s2, 980.665 cm/s2
Standard Atmosphere 101325 N/m2, 1013250 dyn/cm2
Thermochemical calorie 4.184 J, 4.184 x 10e+7 ergs
Litre 0.001 cubic metre
Mole (mol) Amount of substance comprising as many elementary units as there are atoms in 0.012 kg of C12
Inch 0.0254 m, 2.54 cm.
Pound (avdp) 0.45395237 kg, 453.59237 g.