Calorimetric Determination of Differential Heats of Absorption of Hydrogen by Palladium

Abstract

Differential heats of absorption of hydrogen by palladium have been measured with an adiabatic calorimeter. For the first time calorimetric heats have been determined for bulk palladium in the single phase, α and β, regions. The heat of absorption in the α-phase (25°C) was found to be 23.32 ± 4.45 kJ (mol H2)–1 and in the β-phase the isosteric heats decrease with hydrogen content from 46.5 (H-to-Pd = 0.61) to 27.3(H-to-Pd = 0.69). (The measured differential (adiabatic) heats have been corrected for compression work to give isosteric heats.) Heats of sorption determined in the α-phase of palladium black reflect contributions due to both absorption and chemisorption of hydrogen. Some preliminary heats of sorption are also reported at – 78°C and at –195°C with palladium black.