Determination of thermodynamic stability of lanthanum chloride hydrates (LaCl3⋅xH2O) by dynamic transpiration method
Determination of thermodynamic stability of lanthanum chloride hydrates (LaCl3⋅xH2O) by dynamic transpiration method
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DOI：
10.1016/j.jallcom.2013.11.115
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发表时间：
2014-03
影响因子：
6.2
通讯作者：
D. Sahoo;R. Mishra;H. Singh;N. Krishnamurthy
中科院分区：
文献类型：
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作者：
D. Sahoo;R. Mishra;H. Singh;N. Krishnamurthy
用热重技术研究了LaCl3⋅7H2O(S)的分解规律。在313~413K温度范围内，LaCl3⋅7H2O(S)通过生成LaCl3⋅3H2O(S)、LaCl3⋅H2O(S)和LaCl3(S)进行热分解。用动态蒸腾技术测定了LaCl3⋅7H2O(S)及其中间产物的热力学稳定性。进行了两组独立的实验来测量每一步的蒸汽压。水在LaCl3-⋅-7H2O(S)、LaCl3-⋅-3HO(S)和LaCl3-⋅-H2O(S)上的平均蒸汽压分别为：Ln p H2O/atm(±0.02)=−7422(±2 11)/T+17.5(±0.6)(32 7⩽T/K⩽334)，Ln p H2O/atm(±0.02)=−8287(±566)/T+17.5(±1.5)(365⩽T/K⩽369)和ln p H2O/atm(±0.01)=−8566(±346)/T+16.4(±1)(391和lt；T/K<；396)。由蒸气压数据得到LaCl3⋅7H2O(S)、LaCl3⋅3H2O(S)和LaCl3⋅H2O(S)的标准摩尔生成能为：Δf G°(LaCl3⋅7H2O，S)=−3226(±13)+1.6(±0.1)T(327⩽T/K<；Δf G°(LaCl3⋅3H2O，S)=−2006(±11)+0.8(±0.1)T(365⩽T/K⩽369)和Δf G°(LaCl3⋅H2O，S)=−1383(±10)+0.4(±0.01)⋅T(391<；T/K<；396)，kJ−1。
The decomposition pattern of LaCl 3⋅ 7H 2 O (s) was studied by thermogravimetric technique. Thermal decomposition of LaCl 3⋅ 7H 2 O (s) proceeded through the formation of LaCl 3⋅ 3H 2 O (s), LaCl 3⋅ H 2 O (s) and LaCl 3 (s) in the temperature range 313 to 413 K. Thermodynamic stability of the LaCl 3⋅ 7H 2 O (s) and its intermediate products were determined by measuring the vapor pressure of water over the compounds employing dynamic transpiration technique. Two independent sets of experiments were carried out to measure the vapor pressure of each step. The average vapor pressure of H 2 O (g) over LaCl 3⋅ 7H 2 O (s), LaCl 3⋅ 3H 2 O (s) and LaCl 3⋅ H 2 O (s) could be expressed by the relations: ln p H 2 O/atm (±0.02)=− 7422 (±211)/T+ 17.5 (±0.6)(327⩽ T/K⩽ 334), ln p H 2 O/atm (±0.02)=− 8287 (±566)/T+ 17.5 (±1.5)(365⩽ T/K⩽ 369) and ln p H 2 O/atm (±0.01)=− 8566 (±346)/T+ 16.4 (±1)(391< T/K< 396). The standard molar Gibbs energy of formation of LaCl 3⋅ 7H 2 O (s), LaCl 3⋅ 3H 2 O (s) and LaCl 3⋅ H 2 O (s) derived from the vapor pressure data are found to be: Δ f G°(LaCl 3⋅ 7H 2 O, s)=− 3226 (±13)+ 1.6 (±0.1) T (327⩽ T/K< 334), Δ f G°(LaCl 3⋅ 3H 2 O, s)=− 2006 (±11)+ 0.8 (±0.1) T (365⩽ T/K⩽ 369) and Δ f G°(LaCl 3⋅ H 2 O, s)=− 1383 (±10)+ 0.4 (±0.01)⋅ T (391< T/K< 396), kJ mol− 1, respectively.