Pressure Dependence of Viscosity of Polar Gases

Abstract

Viscosity of polar gases, such as steam and ammonia, decreases with increasing pressure. In order to explain this anomaly, we considered a polar gas to be a mixture of dimers and monomers. The viscosity of steam and ammonia was calculated as the sum of mixture term ηₘᵢₓ and collisional transfer term ηc, namely η＝ηₘᵢx+ηc. The calculated and experimental values of viscosity of these gases agreed qualitatively well, and the negative pressure dependence of viscosity of these gases was explained with reasonable success by the theory of association.