Environmental Engineering Reference
In-Depth Information
dence of the self-diffusion coefficient as
D
0
T
300
γ
,
D
D
(4.62)
where the gas temperature
T
isgiveninKelvin.Itshouldbenotedthatwithin
the framework of the hard-sphere model according to (4.60)
1.5, since at a
constant pressure (4.11) gives that the number density of atoms is inversely pro-
portional to the gas temperature. Comparison of this value with that following from
the results of measurements [31, 32], given in Table 4.3, shows the validity of the
hard-sphere model for the self-diffusion coefficient where the numerical coefficient
of (4.62) is
γ
D
1.5.
Table 4.3 contains the parameters in (4.62) for the diffusion coefficients of inert
gases. Note the symmetry of the diffusion coefficient, so the diffusion coefficient
for atomic particles
A
in a gas consisting of atomic particles
B
is equal to the dif-
fusion coefficient of atomic particles
B
in a gas consisting of atomic particles
A
.
The diffusion coefficients for atoms of the first group of the periodic table and for
mercury atoms in inert gases are given in Table 4.4.
γ
D
Ta b l e 4 . 3
The parameter
D
0
in (4.62), which is given in square centimeters per second, is re-
duced to the normal number density and relates to the gas temperature
T
D
300 K. The expo-
nent
γ
in (4.62) is given in parentheses. Data from [31, 32] are used.
Atom, gas He
Ne
Ar
Kr
Xe
He
1.66 (1.73)
1.08 (1.72)
0.76 (1.71)
0.68 (1.67)
0.56 (1.66)
Ne
0.52 (1.69)
0.32 (1.72)
0.25 (1.74)
0.23 (1.67)
Ar
0.195 (1.70)
0.15 (1.70)
0.115 (1.74)
Kr
0.099 (1.78)
0.080 (1.79)
Xe
0.059 (1.76)
Ta b l e 4 . 4
Diffusion coefficients for metal atoms in inert gases at temperature
T
D
300 K,
which are reduced to the normal number density and are expressed in square centimeters per
second [33].
Atom, gas He
Ne
Ar
Kr
Xe
Li
0.54
0.29
0.28
0.24
0.20
Na
0.50
0.31
0.18
0.14
0.12
K
0.54
0.24
0.22
0.11
0.087
Cu
0.68
0.25
0.11
0.077
0.059
Rb
0.39
0.21
0.14
0.11
0.088
Cs
0.34
0.22
0.13
0.080
0.057
Hg
0.46
0.21
0.11
0.072
0.056
