Concentration variations of IR spectroscopic parameters and the structural state of the crystallization medium
| Autor: | B. Z. Volchek, D. A. Medvedeva, E. V. Kir’yanova |
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| Rok vydání: | 2008 |
| Předmět: | |
| Zdroj: | Doklady Physical Chemistry. 422:279-283 |
| ISSN: | 1608-3121 0012-5016 |
| DOI: | 10.1134/s0012501608100096 |
| Popis: | 279 In discussion of mineral formation, ever-increasing attention is being paid to the factor of structuring of the crystallization medium (reviewed in [1]). The experimentally observed anomalies in the physical properties of low-mineralization aqueous solutions are thought of as being related to the “polymorphism” [2] or “polyamorphism” [3] of the water framework. In highmineralization media, the self-organization effects are described by supermolecular and cluster models, including models that imply gradual structural transformations and formation of a special state intermediate between the liquid and crystalline states (see [4, 5] for details). The most comprehensive and diverse information on the structure of a crystal-forming medium can be obtained using a combination of different methods of investigations, including methods that use a crystal as an indicator of the changes in the medium. This approach is justified because of the intimate interaction of a crystal and the medium. This concept is known as the mineral genesis equilibrium law. With the use of the microcrystallization procedure based on this principle, we comprehensively studied the crystal‐aqueous solution phase equilibria in the temperature range 5–50°e [4, 6]. We found multiple anomalies (breaks and extreme points) on liquidus curves (of saturation temperatures) for salt phases (nitratine, potassium nitrate, nitramite, arkanite, tarapacaite, etc.), which are not associated with layer separation in the liquid phase or transformations in the crystalline phase. These anomalies (temperature‐concentration oscillations) are observed in narrow concentration ranges (2‐ 4%) of the salt component and can be as high as 10 K on the temperature scale. Oscillations (or their groups) are, as a rule, associated with definite component ratios in the solution, which correlate with the compositions of the simplest pseudocompounds of the crystal hydrate type. At the same solution compositions, violation of the monotonic behavior of DSC curves is often observed (hereafter, thermal effects) [1]. Detailed studies revealed the existence of oscillations on the concentration dependences of the light scattering and pH of solutions; they correlate with the temperature‐concentration oscillations [4, 6]. The specific features of the properties of solutions as a function of the salt component concentration reflect variations in their structure at the micro- and nanolevels, which are presumably due to |
| Databáze: | OpenAIRE |
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