Polymorphism of anhydrous oxalic acid unravelled

0542947 - FZÚ 2022 RIV GB eng J - Journal Article
Štejfa, V. - Pokorný, V. - Rohlíček, Jan - Fulem, M. - Růžička, K.
Polymorphism of anhydrous oxalic acid unravelled.
Journal of Chemical Thermodynamics. Roč. 160, Sep (2021), č. článku 106488. ISSN 0021-9614. E-ISSN 1096-3626
R&D Projects: GA MŠMT(CZ) EF16_019/0000760
Grant - others:OP VVV - SOLID21(XE) CZ.02.1.01/0.0/0.0/16_019/0000760
Institutional support: RVO:68378271
Keywords : oxalic acid * polymorphism * calorimetry * vapor pressures * x-ray powder diffraction
OECD category: Condensed matter physics (including formerly solid state physics, supercond.)
Impact factor: 3.269, year: 2021
Method of publishing: Limited access
https://doi.org/10.1016/j.jct.2021.106488

Despite being a very common compound in the industry as well as in the nature, the thermodynamic description of oxalic acid is far from being complete and reliable. The literature is contradictory considering both preparation of the two known polymorphs and the triple point temperature above which β-form should be more stable. The published vapour pressure data for α-phase show also a considerable disagreement. In this work, the polymorphs of anhydrous oxalic acid are subjected to a combined thermodynamic and X-ray diffraction study since a single technique cannot give an exhaustive answer on the phase behaviour of the compound. The simultaneous correlation procedure that combines vapour pressure data, calorimetric phase-transition properties, and heat capacities of the crystalline and ideal-gas phase is used to develop a consistent thermodynamic description. Finally, the triple point temperature and transition enthalpy are derived.
Permanent Link: http://hdl.handle.net/11104/0320270