Measurements of the Viscosity of Parahydrogen

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Abstract
The coefficient of shear viscosity η of parahydrogen has been measured by the torsional crystal method at temperatures from 14° to 100°K and at pressures up to 345 atm. Twenty compressed fluid isotherms encompass the density range 0.003–0.087 g/cm3 and include the critical region. The precision and accuracy of the measurements is about 0.5%. The temperature dependence of η changes sign at a density approximately twice the critical density. The viscosity at the critical point is estimated to be 35.5±0.5×10−6 g/cm·sec. The viscosity of saturated liquid normal hydrogen is up to 5% greater than that of parahydrogen at the same temperature. Data of this report have been represented within experimental error by an empirical equation of the form η=η0(T)+A(ρ) expB(ρ)/T, where η0(T) is the viscosity in the low‐density limit and A(ρ) and B(ρ) are density‐dependent coefficients.