Study of the spontaneous crystallization of Na2SO4·7H2O and Na2SeO4·7.5H2O
Study of the spontaneous crystallization of Na2SO4·7H2O and Na2SeO4·7.5H2O
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Na2SO4·7H2O和Na2SeO4·7.5H2O自发结晶的研究
DOI：
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
Stoyan Kamburov
中科院分区：
文献类型：
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作者：
C. Balarew;S. Tepavitcharova;Stoyan Kamburov
研究了温度、冷却速率和溶液浓度对Na2SO4·7H2O和Na2SeO4·7.5H2O从过饱和溶液中自发结晶的影响。研究发现，Na2SO4·7H2O 的结晶几乎总是先于 Na2SO4·10H2O 的结晶发生（高冷却速率除外），而 Na2SeO4·7.5H2O 的结晶则受到相当程度的阻碍。对各自样品中 SO42−/SeO42− 离子 υ1 振动的拉曼光谱研究表明，完全对称的 υ1 振动按以下顺序转移到较高频率：υ1（Na2SO4 溶液）<υ1（Na2SO4·7H2O）<υ1（Na2SO4·10H2O）<υ1（Na2SO4）和 υ1（Na2SeO4）溶液) < υ1 (Na2SeO4·7.5H2O) < υ1 (Na2SeO4·10H2O) < υ1 (Na2SeO4)，分别是 SO42− 和 SeO42− 离子变形增加顺序的证据。这一事实有理由假设相应溶液的结构与亚稳态Na2SO4·7H2O和Na2SeO4·7.5H2O的结构之间存在比它们的十水合物更接近的结构。这样，可以解释与Na2SO4·10H2O、Na2SeO4·10H2O相比，Na2SO4·7H2O、Na2SeO4·7.5H2O的优选结晶。与 Na2SO4·7H2O 相比，Na2SeO4·7.5H2O 的结晶受阻可能是由于其晶体结构（单斜空间群 C2/c）的对称性低于 Na2SO4·7H2O（四方空间群 P41212）。图形摘要
The effects of temperature, cooling rate, and solution concentration on the spontaneous crystallization of Na2SO4·7H2O and Na2SeO4·7.5H2O from their supersaturated solutions was studied. It was found that the crystallization of Na2SO4·7H2O almost always occurs prior to that of Na2SO4·10H2O (except at high cooling rates), while the crystallization of Na2SeO4·7.5H2O is rather hindered. Raman spectroscopic studies on υ1 vibrations of SO42−/SeO42− ions in their respective samples revealed that the totally symmetric υ1 vibrations are shifted to the higher frequencies in the order: υ1 (Na2SO4 solution) < υ1 (Na2SO4·7H2O) < υ1 (Na2SO4·10H2O) < υ1 (Na2SO4) and υ1 (Na2SeO4 solution) < υ1 (Na2SeO4·7.5H2O) < υ1 (Na2SeO4·10H2O) < υ1 (Na2SeO4), respectively, which is an evidence of the order in which the deformation of the SO42−, respectively, SeO42− ions, increases. This fact gives grounds to assume the existence of a closer proximity between the structures of the corresponding solutions and those of the metastable Na2SO4·7H2O and Na2SeO4·7.5H2O, than with their decahydrates. In this way, the preferred crystallization of Na2SO4·7H2O, respectively, Na2SeO4·7.5H2O, in comparison with that of Na2SO4·10H2O, respectively, Na2SeO4·10H2O, can be explained. The hindered crystallization of Na2SeO4·7.5H2O in comparision with that of Na2SO4·7H2O may be attributed to the lower symmetry of its crystal structure (monoclinic space group C2/c) in comparison with that of Na2SO4·7H2O (tetragonal space group P41212).Graphical abstract
影响因子：
15
作者：
I. Oswald;A. Hamilton;C. Hall;W. G. Marshall;T. Prior;C. Pulham
通讯作者：
I. Oswald;A. Hamilton;C. Hall;W. G. Marshall;T. Prior;C. Pulham