Titanium melting curve: data consistency assessment, problems and achievements

Experimental data for the thermodynamic properties of titanium on the melting curve in the pressure range from atmospheric value to 90 GPa are analyzed and brought into correspondence. The problems that have been considered are (i) the lack of data for the solid $\beta$-phase density near the normal melting point and (ii) the formation probability of a triple point on the melting curve for the coexisting $\beta$-, $\omega$-, and liquid phases of titanium. To estimate the change of the volume upon melting $3d$ elements from Mendeleev's periodic system, a correlation between the change of the volume, $\Delta V_m$, and the change of the entropy, $\Delta S_m$, on the melting curve at atmospheric pressure is suggested and effectively used.