Accurate measurements of the viscosity of water in the temperature range 19.5–25.5°C

The viscosity of water has been measured with high accuracy in the temperature range 19.5–25.5°C, using an absolute oscillation viscometer. The resulting data are represented by the modified Arrhenius expression In (η/mPa s) = 1.85191 - 3201.27 K/T + 779359 K2/T2. The viscosity of water at 20°C and atmospheric pressure is 1.0006 mPa s ± 0.05% at the 68% confidence level. This value is 0.13% lower than the currently recommended value at 20°C: 1.002 ± 0.001 mPa s.