The viscosity of liquid and gaseous mercury has been measured at saturation conditions and in the expanded gas phase to 1520 K and nearly 1000 bar. Measurements were performed with an oscillating cup viscometer. Small cylindrical, closed autoclaves (“cups”) of tungstenrhenium or pure molybdenum were suspended inside a heated vacuum chamber on tungsten rhenium wires. The viscosity at 1520 K is 0.58mPa · s in the saturated liquid and 0.16 mPa · s in the saturated gas phase as compared with 2.0 mPa · s for liquid Hg at the melting point. Results are discussed in terms of a modified Enskog hard‐sphere transport theory for dense fluids. An internally consistent description of data is obtained with temperature‐dependent hard‐sphere diameters of Hg atoms and ions derived from PVT and neutron scattering data. A viscosity curve for mercury along the whole coexistence line to the critical point (Tc = 1760 K) is given. The analysis is applied to correlate data for fluid Hg, Pb and Na.

The viscosity of cesium at 1620 K and 40 bar has been determined to 41· 10−6 (Pa· s) by the oscillating cup method. The saturated vapor density at 1580 K could be derived from the viscosity measurements. The viscosity of liquid gallium has been determined from 370 K to 1800 K. The experimental results have been compared with calculations based on the Enskog hard‐sphere transport theory for dense fluids.

The viscosities and the self-diffusion coefficients of expanded fluid mercury and caesium have been calculated as a function of pressure and temperature up to their critical points with the aid of a modified Enskog theory. The results are compared with the transport coefficients of other liquid metals and of non-polar and polar fluids applying the principle of corresponding states. The thermal conductivities of fluid metals along the full coexistence line are also discussed. A classification of the transport phenomena in fluids with various types of interaction forces - including expanded fluid metals - is given

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