INTERNATIONAL EQUATIONS FOR THE PRESSURE ALONG THE MELTING AND ALONG THE SUBLIMATION CURVE OF ORDINARY WATER SUBSTANCE

In order to define the phase boundary between the solid phase (ice) and the fluid phase (liquid and gas) of ordinary (light) water substance in pressure-temperature coordinates, correlation equations for the pressure along the melting curve of the various modifications of ice as well as for the pressure along the sublimation curve are presented. The five equations for the melting pressure of the ice phases ice I, ice III, ice V, ice VI, and ice VII, which only contain one to three fitted coefficients, cover the pressure range from the ''normal'' triple point to 20000 MPa. In this entire range the equations represent the selected measurements of the melting pressure within their experimental uncertainty. The 2-coefficient equation for the sublimation pressure covers the temperature range from 190 K to the triple point (273.16 K). The equations correspond to the new International Temperature Scale of 1990 (ITS-90). All these equations form the basis of the revised release on the pressure along the melting and sublimation curves of ordinary water substance. A verbatim copy of this release is presented in the Appendix of this paper.