Vapour pressure of water

Water supercooled below its normal freezing point has a higher vapor pressure than that of ice at the same temperature and is, thus, unstable.

Here is a comparison of the accuracies of these different explicit formulations, showing saturation vapor pressures for liquid water in kPa, calculated at six temperatures with their percentage error from the table values of Lide (2005): A more detailed discussion of accuracy and considerations of the inaccuracy in temperature measurements is presented in Alduchov and Eskridge (1996).

The analysis here shows the simple unattributed formula and the Antoine equation are reasonably accurate at 100 °C, but quite poor for lower temperatures above freezing.

As expected,[clarification needed] Buck's equation for T > 0 °C is significantly more accurate than Tetens, and its superiority increases markedly above 50 °C, though it is more complicated to use.

However, there are more recent reviews of possibly superior formulations, notably Wexler (1976, 1977),[5][6] reported by Flatau et al.