Thermodynamics of Vaporization and High Temperature Enthalpy of Zirconium Tetraiodide

Abstract

The sublimation of ZrI4 was studied by a torsion effusion-gravimetric technique in which the molecular weight of the effusing gas and its pressure in the effusion cell were measured simultaneously. The sublimation pressures of ZrI4 were found to depend on the orifice size of the effusion cell. The measured pressures were extrapolated to zero orifice size to obtain the equilibrium vapor pressures, which could be represented by the equation -+-86log P(ZrI4, atm) ----9.79 • 0.19 --.(from 410 ~ to 480~ T Enthalpies above room temperature, up to 703.1~ for solid zirconium tetraiodide were measured in a copper-block, drop calorimeter. The enthalpy increments above 298.15~ were expressed by the equation HT ~ --H29s ~ (kcal/mole) = 29.

Thermodynamics of the Gaseous Zirconium Iodides

“…ZrI4(g).--The thermodynamic functions, based on accurately known spectroscopic and molecular constants, were taken from the JANAF Tables (3). We have adopted the enthalpy of sublimation and enthalpy of formation of the gas, AHf~ ----84.9 -+ 1.5 kcal/ mole, given by Cubicciotti et al (7).…”

Thermodynamics of Vaporization of ZrI4 from Substoichiometric Solid Zirconium Iodides

“…The ZrI2.4 was made as follows. High purity (Ventron Corporation) zirconium foil was sealed into a quartz glass tube under the vacuum with ZrI4 prepared as described earlier (7). The tube was heated at 500~ for about one week.…”

“…and the method of operation used in this work were the same as those described in our earlier publication (7). Two series of effusion measurements were made with cells of different orifice size which were those labeled cell A (0.0473 cm orifice diam) and cell B (0.0803 cm orifice diam) in the earlier report, which also gives the other cell geometries and characteristics.…”

Kinetic study of reaction between zirconium and iodine

“…The thermochemical aspect of this problem has been studied in detail by D. Cubicciotti and co-workers [4][5][6] and progress in this area is reported in several publications. Taking the thermodynamic data into consideration, Gotzman [13] proposed that the critical iodine partial pressure, deduced by Hofmann et.…”