Viscosity of xenon and ethane in the critical region

Abstract

The viscosity of xenon has been measured along 10 isochores and the viscosity of ethane along five isochores in the region of the gas‐liquid critical point. The viscometer was a torsionally oscillatingquartz cylinder, which generates a viscous wave when immersed in a fluid; the resonant properties of the quartz in a viscous fluid can be related to the viscosity‐density product of the fluid. The viscosities of both substances exhibit an ``anomalous'' increase which can be fitted to an equation of the form Δη/η id = A ln[(T−Tc/Tc ]+B. This functional form is in agreement with recent theoretical predictions by Sengers, and values of the coefficient A obtained from the data are consistent with theoretical analysis which shows A = −8ν/15π2, where ν is the usual critical state exponent describing the divergence of the long range correlation length. Measuredviscosity excesses amount to 15% for xenon and 16% for ethane. The critical temperatures and densities have been determined to be Tc =16.627±0.005°C, ρ c =1.11±0.01 g/cm3 for xenon; Tc =32.218±0.005°C, ρ c =0.2055±0.002 g/cm3 for ethane.