Triple Point of Pure and Impure Deuterium

The liquidus-point behaviour of high-purity and impure D 2 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; D 2 samples doped with as much as 1% H 2 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 D 2 were found to be 18.696 3 K and 18.731 9 K respectively; the normal boiling point of equilibrium D 2 was found to be 23.636 9 K; the heat of fusion was measured as 49.53 J/g; and the density of D 2 gas at the triple-point temperature and pressure for normal D 2 is 4.61 g/cm 3 . The vapour pressure of equilibrium D 2 between its normal boiling and triple points can be well described by a polynomial of the form ln ( P / P 0 ) = ∑ i =−1 4 a i ( T − T 0 ) i