Investigation of metastable zone width of ammonium oxalate aqueous solutions
Investigation of metastable zone width of ammonium oxalate aqueous solutions
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DOI：
10.1002/crat.200800545
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发表时间：
2009-04
影响因子：
1.5
通讯作者：
K. Sangwal;K. Wójcik
中科院分区：
文献类型：
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作者：
K. Sangwal;K. Wójcik
用多温法研究了纯草酸铵水溶液介稳区宽度（最大过冷度ΔTmax）与冷却速率R和饱和温度T0的关系。实验结果进行了讨论，通过使用两个最近的先进的方法：（1）自洽的Nynovlt-类方法的基础上的成核速率J和最大过饱和度lnSmax之间的幂律关系，和（2）一种新的方法的基础上的J和lnSmax之间的关系所描述的经典的三维成核理论。实验数据的分析表明，这两种方法可靠地描述了亚稳区宽度的实验数据，并提供了有用的信息的物理过程和成核动力学参数。对于相当可溶的化合物来说，这两种方法预测的各种物理量的值都是合理的。通过多温法和密度测量获得的ΔTmax作为T0的函数的数据的仔细检查表明，ΔTmax具有随着饱和温度T0的增加而减小的轻微趋势。在饱和温度303 K时的lnSmax值表明草酸铵水溶液的介稳区宽度是由多温法中的初级成核和密度测量过程中的次级成核决定的。（© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA，魏因海姆）
The metastable zone width of pure ammonium oxalate aqueous solutions, as represented by maximum supercooling ΔTmax, is investigated as functions of cooling rate R and saturation temperature T0 by the polythermal method. The experimental results are discussed by using two recently advanced approaches: (1) self‐consistent Nývlt‐like approach based on a power‐law relationship between nucleation rate J and maximum supersaturation lnSmax, and (2) a novel approach based on the relationship between J and lnSmax described by the classical three‐dimensional nucleation theory. Analysis of the experimental data revealed that both approaches describe the experimental data on metastable zone width by the polythermal method reliably and provide useful information about the physical processes and parameters involved in nucleation kinetics. The values of various physical quantities predicted by both of these approaches are reasonable for a fairly‐soluble compound. A careful examination of the data on ΔTmax as a function of T0 obtained by polythermal method and from density measurements showed that ΔTmax has a slight tendency to decrease with increasing saturation temperature T0. The values of lnSmax at saturation temperature 303 K suggest that the metastable zone width of ammonium oxalate aqueous solutions is determined by primary nucleation in the polythermal method and by secondary nucleation during density measurements. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)