Phase transition between two anhydrous modifications of NaHSO₄ mediated by heat and water

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• 作者：Christopher D. Zangmeister ; Jeanne E. Pemberton
• 关键词：α ; -NaHSO₄ ; β ; -NaHSO₄ ; Phase transition ; Raman spectroscopy ; Differential scanning calorimetry
• 刊名：Journal of Solid State Chemistry
• 出版年：2007
• 出版时间：June 2007
• 年：2007
• 卷：180
• 期：6
• 页码：1826-1831
• 全文大小：247 K

文摘

The phase transition between the two anhydrous modifications of NaHSO₄ (α and β) was studied using Raman spectroscopy and differential scanning calorimetry. These measurements indicate that β-NaHSO₄ is a metastable phase and readily undergoes phase transition to thermodynamically stable α-NaHSO₄ with an exothermic enthalpy change of 3.5 kJ/mol. Both thermal (temperatures >434 K) and chemical (exposure to H₂O) pathways were identified for this transition. The transition is irreversible, and α-NaHSO₄ is an intermediate phase between β-NaHSO₄ and NaHSO₄·H₂O. The possible mechanism of the phase transition is discussed.