Double Anomalous Peak in the Heat Capacity Just Below the Triple Point of Saturated e-H2 with FeO(OH)

The heat capacity of e-H 2 with powder of FeO(OH) used as a catalyst for ortho-para equilibration has been investigated using sealed cells fabricated at the National Institute of Standards and Technology and at the National Metrology Institute of Japan. An anomalous double peak has been observed in their heat capacities at temperatures just below the triple point independent of sources of H2 and FeO(OH) and designs of sealed cells. Supercooling behavior has been observed not only at the triple point but also at each anomalous peak resulting from a depression of the melting temperature of a portion of solid H 2 in close physical proximity to the catalyst. The reduction of the amount of catalyst suppresses the size of the anomalies and allows one to obtain more reliable melting curves for e-H2 at the triple point.