Vapor Pressure of Zirconium Tetrafluoride

Measurements were made of the vapor pressures of zirconium tetrafluoride by using a torsion effusion apparatus. The temperature dependence fit the equation: log(p/Pa) = (15.20 +/- 0.15) - (11 900 +/- 200)/(T/K) (from 685 to 828 K). The compound vaporizes congruently in the monomeric form. With treatment of the measured vapor pressures by second- and third-law methods, the standard sublimation enthalpy Delta H-sub degrees(298 K) = (239 2) kJ . mol(-1) was obtained