TRIPLE POINT OF PURE AND IMPURE DEUTERIUM

The liquidus-point behavior of high-purity and impure D2 has been studied in both normal and equilibrium states. It was found that the liquidus point in the limit of vanishing amount of condensed phase is nearly impurity independent; D2 samples doped with as much as 1% H2 had liquidus points only about 2 mK different from the purest samples available. The temperatures (on the IPTS-68) for the triple points of equilibrium and normal D2 were found to be 18.6963 K and 18.7319 K respectively; the normal boiling point of equilibrium D2 was found to be 23.6369 K; the heat of fusion was measured as 49.53 J/g; and the density of D2 gas at the triple-point temperature and pressure for normal D2 is 4.61 g/cm3. The triple point of deuterium could be useful for a fixed point on a practical temperature scale.