Minimum heat of formation of potassium iodo hydride

It was previously reported (R. Mills et al., Synthesis and characterization of potassium iodo hydride, Int. J. Hydrogen Energy, 25(12) (2000) 1185) th at a novel inorganic hydride compound KHI which comprised a high binding en ergy hydride ion was synthesized by reaction of atomic hydrogen with potass ium metal and potassium iodide. Potassium iodo hydride was identified by ti me of flight secondary ion mass spectroscopy, X-ray photoelectron spectrosc opy, H-1 and K-39 nuclear magnetic resonance spectroscopy, Fourier transfor m infrared spectroscopy, electrospray ionization time of flight mass spectr oscopy, liquid chromatography/mass spectroscopy, thermal decomposition with analysis by gas chromatography, and mass spectroscopy, and elemental analy sis. We report measurements of heats of formation of KHI by differential sc anning calorimetry (DSC) on a very reliable commercial instrument, a Setara m HT 1000 calorimeter. With reactant KI present, potassium metal catalyst a nd atomic hydrogen were produced by decomposition of KH at an extremely slo w rate under a helium atmosphere to increase the amount of atomic hydrogen by slowing the rate of molecular hydrogen formation. Since not all of the s tarting materials reacted, the observed minimum heats of formation were ove r -2000 kJ/mol H-2 compared to the enthalpy of combustion of hydrogen of -2 41.8 kJ/mol H-2. (C) 2001 International Association for Hydrogen Energy. Pu blished by Elsevier Science Ltd. All rights reserved.