Melting temperature of ice at positive and negative pressures

The pressure of an equilibrium mixture of water and ice contained in helically wound Pyrex capillary tubes was measured as a function of temperature. The sealed helices function as Berthelot tubes, allowing the measurements to extend to negative pressures, and as pressure gauges using the Bourdon tube principle. The locus of the melting line for ice I was measured up to 1500 bar and extended, for the first time, into the negative pressure region. Results are reported to -240 bar for H2O and to -150 bar for D2O. The locus of the melting line at negative pressure is discussed