Melting Curves of ${\mathrm{H}}_2$, ${\mathrm{D}}_2$, and ${\mathrm{T}}_2$ up to 3500 kg/${\mathrm{cm}}^2$

The melting pressure-temperature relationship of the three hydrogen isotopes has been determined accurately to 3500 kg/${\mathrm{cm}}^2$ by the blocked-capillary method. The data were fitted with fair success to the Simon-type equation, $P=a+b{T}^c$. The melting curves of ${\mathrm{H}}_2$, ${\mathrm{D}}_2$, and ${\mathrm{T}}_2$ are displaced downward on the pressure axis in that order and, at identical temperatures, exhibit approximately equal slopes.