Analytical representations of the phase equilibrium curve of the water–vapor system

A brief critical analysis of the theoretical $P(T)$ liquid–vapor phase equilibrium curves is given. Based on the Clapeyron–Clausius equation and data on the heat capacity of water, a two-parameter expression of the $P(T)$ curve is obtained for water in the temperature range from the triple point to $389$ K. The parameters of the $P(T)$ curve are determined from data on the pressure and heat of evaporation of water at the triple point. The accuracy of the $P(T)$ function is comparable to the actual accuracy of standard thermodynamic tables for water and water vapor.