Heats of formation of zirconium hydrides

Heats of solution in 3.83N HF have been measured for zirconium metal and for five zirconium hydrides to evaluate the following heats of formation AHf0298: ZrH2 -39.7, ZrH1.85 -38.2, ZrH1.70. -34.7, ZrH1.43 -30.05, ZrH1.23 -25.3 kcal/mole hydride. A review of heat capacity and entropy data for zirconium hydrides has enabled a good correlation to be made between calorimetric and dissociation pressure studies, so that the effect of composition on all thermodynamic properties is established.