差示扫描量热法
等温过程
热分解
焓
分解
相变
化学
热力学
相(物质)
公式单位
分析化学(期刊)
材料科学
结晶学
晶体结构
有机化学
物理
作者
Michael E. Brown,Leslie Glasser,James A. Larson
标识
DOI:10.1016/0040-6031(79)85057-1
摘要
Phase transitions and the thermal decomposition of KH2PO4 have been examined from room temperature to above 300°C by means of hot-stage microscopy, isothermal gravimetry and differential scanning calorimetry. Phase transitions at 198 and 242°C are confirmed, with corresponding enthalpy changes 4.2 and 2.3 kJ mole−1, but no evidence has been found of a transition reported near 110°C. The thermodynamic and other evidence suggest a structural change at 198°C while the change at 242°C is less profound, perhaps involving only changes in the form of the hydrogen bonding. Thermal decomposition occurs in four stages, under conditions of free vapour escape, with the loss of one-quarter of a mole of water per formula unit of KH2PO4 in each stage. The products of each stage of decomposition are tentatively identified.
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