Isotopic Effect on the Melting Point of Lithium Nitrate

Abstract

The techniques of segregation during normal freezing and of zone melting have been used to establish that the melting point of 6LiNO3 is higher than that of 7LiNO3. The difference is of the order of 0.03 °C. The isotope shift of the melting point is in the opposite direction of the isotope effects found previously for phase transitions in solid lithium metal and lithium sulfate. For the latter salt a recalculation based on a more accurate value for the self-diffusion coefficient shows that the temperature of transition at about 575 °C to a fee structure is about 0.08 degr. lower for 6Li2SO4 than for 7Li2SO4.

Thermodynamic Analysis of Isotope Effects on Triple Points and/or Melting Temperatures

“…It is highly implausible. On the other hand, the earlier and much smaller 6Li/7Li TPIE re ported by Jansson and Lunden [51] for this compound turns out to be equivalent to a much smaller blue shifts on fusion, (« 3 x 2 cm "x), and is consistent with the spectroscopic analysis. We conclude that it is the latter MPIE [51] which is the more reliable.…”

“…They lead to the conclusion that the MPIEs reported by HL are in error. HL themselves comment that their DSC mea surements yield MPIEs which are an order of magni tude or more larger than earlier reports based on measurements of solid/liquid fractionations [51]. The present discussion indicates that it is those earlier re sults which are more likely correct.…”