The viscosity of polar gases at normal pressures

The viscosity behavior at normal pressures (0.2 to 5 atm.) of fifty‐three polar gases was examined, and equations representing the dependence of viscosity on temperature for these gases were developed. A dimensional analysis approach was applied to the variables effecting the viscosity of polar gases at moderate pressures. These variables were assumed to be the molecular weight, temperature, and the critical constants of the substance. Reliable viscosity data available in the literature for the polar gases investigated were utilized to determine the exact dependence of their viscosities on these variables. In contrast to the results of a previous study, which show that for nonpolar gases the viscosity parameter μ*ξ (where ξ = T c ⅙ / M ½ P c ⅔ ) is independent of z c ; the results of the present study indicate that for polar gases this parameter is dependent on z c . The viscosity parameters of gases which exhibit hydrogen bonding were found to depend uniquely on z c 5/4 and reduced temperature, while the remaining polar gases were found to exhibit a different unique dependence on z c ⅔ and reduced temperature. For these two classes of polar substances separate viscosity relationships were developed. For eleven gases which exhibit hydrogen bonding viscosities were calculated and compared with corresponding experimental values. An average deviation of 1.47% resulted from 129 experimental points. For the other polar gases the calculated values were also compared with experimental values and produced an average deviation of 2.59% for 197 experimental points.