Mass spectrometric studies at high temperatures: XVII. Sublimation and vapor pressures of Dy(III), Ho(III) and Er(III) fluorides

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The sublimation and vapor pressures of DyF 3, HoF 3 and ErF 3 were measured mass-spectrometrically and by semimicrobalance Knudsen studies. DyF 3, HoF 3, and ErF 3 were established as the major vapor species over the respective solid 01 molten trifluorides by mass-spectrometric work. The results are represented for DyF 3 by: log P sub. (atm) = − (2.325 ± 0.031) × 10 4 T + 10.720 ± 0.229 log P vap. (atm) = − (1.842 ± 0.032) × 10 4 T + 7.538 ± 0.209 , for HoF 3 by log P sub. (atm) = − (2.309 ± 0.033) × 10 4 T + 10.650 ± 0.245 log P vap. (atm) = − (1.847 ± 0.048) × 10 4 T + 7.333 ± 0.330 , and for ErF 3, by log P sub. (atm) = − (2.339 ± 0.054) × 10 4 T + 10.680 ± 0.391 log P vap. (atm) = − (1.930 ± 0.027) × 10 4 T + 7.777 ± 0.186 where errors noted are standard deviations from the least-squares fits. The heats of sublimation and vaporization are : for DyF 3 ΔH sub. (1356° K) = 106.4 ± 1.5 kcal mole −1 ΔH vap. (1523° K) = 84.3 ± 1.5 kcal mole −1 for HoF 3 ΔH sub. (1366° K) = 105.6 ± 1.5 kcal mole −1 ΔH vap. (1465° K) = 84.5 ± 2.2 kcal mole −1 for ErF 3 ΔH sub. (1373° K) = 107.0 ± 2.5 kcal mole −1 ΔH vap. (1461° K) = 88.3 ± 1.2 kcal mole −1