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Composition, Structure, and Thermal Properties of Potassium Acetate Hydrates
Paulina Kalle1, Stanislav I Bezzubov1, Egor V Latipov2
1Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russia.
Inorganic Chemistry
|January 17, 2025
Summary
This study reveals new crystal structures for potassium acetate (KOAc) hydrates, correcting century-old misconceptions about their composition and properties. These findings provide crucial structural data for this industrially relevant compound.
Area of Science:
- Crystallography
- Materials Science
- Solid-state Chemistry
Background:
- The properties of compounds are dictated by their crystal structure.
- Potassium acetate (KOAc) and its hydrates are industrially relevant but poorly understood due to limited structural data.
- Previous understanding of KOAc hydrates at ambient temperature was based on incorrect compositions.
Purpose of the Study:
- To determine the crystal structures of potassium acetate polymorphs and hydrates.
- To accurately characterize the composition of KOAc hydrates.
- To elucidate the phase transitions and hydration-dehydration processes of KOAc.
Main Methods:
- Single-crystal and powder X-ray diffraction (XRD).
- Variable-temperature XRD.
- Thermal analyses (e.g., TGA/DSC).
- Accurate determination of water content in crystal hydrates.
Main Results:
- The crystal structures of KOAc polymorphs and hydrates were determined for the first time.
- Two new hydrate phases, 3KOAc·2H2O and KOAc·xH2O (x = 0.38-0.44), were identified, replacing the previously assumed "sesquihydrate" and "hemihydrate".
- Phase transitions and hydration-dehydration processes were clearly established using variable-temperature techniques.
Conclusions:
- This research provides the first definitive structural data for potassium acetate hydrates.
- The study corrects long-standing inaccuracies regarding the composition of KOAc hydrates.
- The findings offer fundamental insights into the solid-state chemistry of potassium acetate, crucial for its industrial applications.
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