The rate at which a substance passes through a semipermeable membrane is determined by the diffusivity D (cm 2 /s) of the gas.  D varies with the membrane temperature T ( K ) according to the Arrhenius equation  D = D o exp (-E/RT) .

1. The rate at which a substance passes through a semipermeable
membrane is determined by the diffusivity
D
(cm
2
/s) of the gas.
D
varies with the membrane temperature
T
(
K
) according to the Arrhenius equation
D
=
D
o
exp (-E/RT)