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Equation to estimate the viscosity of gas mixtures at low pressures.
It is a simplification of an extension of the rigorous kinetic theory of Chapman and Enskog to determine the viscosity of multicomponent mixtures, at low pressures and with a factor to correct for molecule shape and polarity.

The input argument Kappa is a special correction for highly polar substances such as alcohols and acids.
Values of kappa for a few such materials:

Compound	Kappa	Compound	Kappa
Methanol	0.215	n-Pentanol	0.122
Ethanol	0.175	n-Hexanol	0.114
n-Propanol	0.143	n-Heptanol	0.109
i-Propanol	0.143	Acetic Acid	0.0916
n-Butanol	0.132	Water	0.076
i-Butanol	0.132

Chung, et al. (1984) suggest that for other alcohols not shown in the table:
    
    kappa = 0.0682 + 4.704*[(number of -OH groups)]/[molecular weight]

S.I. units relation for the debyes: 
                                                       1 debye = 3.162e-25 (J.m^3)^(1/2)

References

[1] THE PROPERTIES OF GASES AND LIQUIDS, Fifth Edition,
          Bruce E. Poling, John M. Prausnitz, John P. O'Connell.
[2] Chung, T.-H., M. Ajlan, L. L. Lee, and K. E. Starling: Ind. Eng. Chem. Res., 27: 671 (1988).
[3] Chung, T.-H., L. L. Lee, and K. E. Starling; Ing. Eng. Chem. Fundam., 23: 3 ()1984).

etaMixture = mixtureViscosityChung(T, Tc, Vcrit, w, mu, MolecularWeights, y, kappa)

T	Type: Temperature (K) Description: Temperature
Tc	Type: Temperature[nX] (K) Description: Critical temperatures
Vcrit	Type: MolarVolume[nX] (m³/mol) Description: Critical volumes (m3/mol)
w	Type: Real[nX] Description: Acentric factors
mu	Type: Real[nX] Description: Dipole moments (debyes)
MolecularWeights	Type: MolarMass[nX] (kg/mol) Description: Molecular weights (kg/mol)
y	Type: MoleFraction[nX] (mol/mol) Description: Molar Fractions
kappa	Default Value: zeros(nX) Type: Real[nX] Description: Association Factors

etaMixture	Type: DynamicViscosity (Pa⋅s) Description: Mixture viscosity (Pa.s)