The viscosity coefficient of gaseous nitrogen was measured with a vibrating-wire viscometer of very high precision. The measurements were performed along the six isotherms of (298.15, 323.15, 348.15, 373.15, 398.15, and 423.15) K and at pressures up to a maximum of 35 MPa. The gas densities needed for the evaluation of the measuring values were calculated using an equation of state by Span et al. (J.

A vibrating-wire viscometer of very high precision was used to measure the viscosity of gaseous ethane. The experimental data were taken at subcritical temperatures of (290 and 300) K up to 88 % of the saturated vapor pressure and at supercritical temperatures of (310, 320, 340, 370, 400, and 430) K at pressures up to a maximum of 30 MPa. The measuring values were evaluated using an equation of state by Bücker and Wagner. The reproducibility is ± (0.05 to 0.1) %, whereas the total uncertainty is estimated to be ± (0.25 to 0.4) % with an increase of (1 to 2) % close to the critical point. The viscosity values of the isotherms were correlated as a function of reduced density using a power series expansion. A comparison with correlations from the literature shows deviations up to about 5 % in the near critical region and up to 2 % at higher densities and temperatures. On the basis of a comparison with direct experimental data from the literature, it is concluded that the new values are the most reliable for the improvement of the viscosity surface correlation of ethane.

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A new variant of the Loschmidt technique has been developed for measuring binary diffusion coefficients in gas mixtures in a temperature range from 10 to 80 °C and for pressures between 0.1 and 1 MPa. The two half cells of the thermostatted diffusion cell have a rectangular cross section and are fixed one upon the other. They can be connected and separated by means of a sliding plate provided with a pneumatically operated seal. The concentration in both half cells is determined simultaneously during the diffusion process using an optical system for holographic interferometry for each. The change in the refractive index results in an interference pattern which is recorded as a function of time. The concentrations of the diffusing components are derived by means of the Lorentz–Lorenz equation. The binary diffusion coefficients are calculated via the integrated ideal diffusion equation for the complete mole fraction range performing only a unique diffusion experiment. The performance of the apparatus is demonstrated on first measurements on the argon–neon system at 293.15 K. Separate refractive index measurements are carried out leading to values for the first refractivity virial coefficient of the pure gases with an estimated uncertainty of ±0.1%. This low uncertainty is required for the aimed uncertainty of ±0.5…1% for the diffusion measurements to determine the concentration and density dependences of the binary diffusion coefficient.

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