Vapor pressure and thermodynamics of octahedral arsenic trioxide (arsenolite)

• Published in: The Journal of chemical thermodynamics 1972-01, Vol.4 (2), p.175-190
• Main Authors: Behrens, Robert G., Rosenblatt, Gerd M.
• Format: Article
• Language: English
• ISSN: 0021-9614; 1096-3626
• DOI: 10.1016/0021-9614(72)90055-9

Knudsen effusion experiments using a recording vacuum microbalance have been performed on powdered arsenic trioxide (arsenolite) over the temperature range 367 to 429 K. The vapor pressure of arsenolite over this range is (R cal th K −1 mol −1) ln( p atm) = − (27759±574) k t + (45.32±1.46). Third-law thermodynamic functions have been approximated for solid arsenolite above 298.15 K. Third-law thermodynamic functions for As 4O 6(g) have been computed using selected vibrational frequencies based upon available spectroscopic measurements on As 4O 6(g), and on arsenolite powder and single crystals. A third-law enthalpy of sublimation, ΔH o(298.15 K) = (28.13 ± 0.20) kcal th mol −1, is obtained. The second-law result is ΔH o(298.15 K) = (28.31 ± 0.56) kcal th mol −1. These results are consistent with data of other authors. The agreement between second-law and third-law enthalpies supports the vibrational assignment used to compute the third-law functions and entropy of As 4O 6(g), S o(298.15 K) = (97.81 ± 2.5) cal th K −1 mol −1.