We present a detailed thermodynamic analysis of the temperature of the ice point as a function of atmospheric pressure. This analysis makes use of accurate international standards for the properties of water and ice, and of available high-accuracy data for the Henrys constants of atmospheric gases in liquid water. The result is an ice point of 273.150 02 K at standard atmospheric pressure, with higher ice-point temperatures (varying nearly linearly with pressure) at lower pressures. The effect of varying ambient CO2 concentration is analyzed and found to be significant in comparison to other uncertainties in the model. The thermodynamic analysis is compared with experimental measurements of the temperature difference between the ice point and the triple point performed at elevations ranging from 145 m to 4302 m, with atmospheric pressures from 101 kPa to 60 kPa.
Proceedings Title: Proceedings of the 9th International Temperature Symposium
Conference Dates: March 19-23, 2012
Conference Location: Anaheim, CA
Pub Type: Conferences
fixed point, Henry's law, ice point, pressure, thermometry