P. D. Kleinschmidt, D. Cubicciotti, D. L. Hildenbrand
1978
Citations
0
Influential Citations
12
Citations
Journal
Journal of The Electrochemical Society
Abstract
The gaseous zirconium iodides ZrI/sub 4/, ZrI/sub 3/, ZrI/sub 2/, and ZrI, generated by the reaction of HI(g) with Zr(s) at elevated temperatures, were identified and characterized thermochemically by Knudsen cell mass spectrometry. Gaseous ZrI/sub 4/ was the major reaction product up to about 1300/sup 0/K; above this temperature, atomic I became the major product, with minor amounts of the lower Zr iodides appearing as the temperature was progressively raised. From an analysis of equilibrium data, the following enthalpies of formation were deduced; ..delta.. Hf/sup 0//sub 298/(ZrI/sub 3/,g) = - 30.8 +- 1.5 kcal/mole, ..delta..Hf/sup 0//sub 298/(ZrI/sub 2/, g) = 32.6 +- 4.0 kcal/mole, and ..delta..Hf/sup 0//sub 298/(ZrI, g) = 96.3 +- 2.8 kcal/mole. Individual bond dissociation energies evaluated from the enthalpy data are close to the average value in ZrI/sub 4/. The new thermochemical data are consistent with observations on the iodide process for refining impure zirconium whereas earlier estimates are not. 4 figures, 7 tables.