Triple Point of Pure and Impure Deuterium

Abstract

The liquidus-point behaviour 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 vapour pressure of equilibrium D2 between its normal boiling and triple points can be well described by a polynomial of the form ln (P/P0) = ∑i=−14 ai(T − T0)i

Recommended values of temperature on the International Temperature Scale of 1990 for a selected set of secondary reference points

“…These problems have now been satisfactorily resolved and the point has been promoted to Table 1. There have been four, more recent, independent determinations of the triple-point temperature [6][7][8][9]202], with the result shown in Table 1. The combined standard uncertainty of the four measurements is 0,3 mK, although the between-set component of the standard deviation is 0,4 mK, indicating that there are probably still some small unresolved systematic uncertainties in at least one of the experiments.…”