Raman studies molten salts

Another system studied by Raman spectroscopy concerns molten salts at room temperature, which usually involve organic compounds. The system consists of... 

Structural studies in fused salts by means of careful and thorough high-temperature measurements of electrical conductivity, density, viscosity, and laser- Raman spectroscopy have been reviewed. Four problem areas are discussed (1) melting mechanisms of ionic compounds with large polyatomic cations, (2) salts as ultra-concentrated electrolyte solutions, (3) structural aspects and Raman spectroscopy, and (4) electrolysis of molten carbonates. The results in these areas are summarized and significant contributions to new experimental techniques for molten-salt studies are discussed.275 The physical properties and structure of molten salts have also been reviewed in terms of operational (hole, free volume, partly disordered crystal) and a priori (intermolecular potential) models.276 Electrochemistry... 

Direct methods for studying the structure of molten salts are X-ray and neutron diffraction analyses, infrared and Raman spectroscopy, NMR (nuclear magnetic resonance) measurement, and also very recently, XAFS (X-ray Absorption Fine Structure) measurement in melts, were developed. Fiowever, the most frequently used direct methods are X-ray and XAFS measurements, Raman spectroscopy, and NMR measurements. Therefore these three methods of direct investigation will be briefly described here. 

Divalent metal halides and their mixtures with alkali metal halides have been among the first molten salt systems to be investigated by Raman spectroscopy. Studies of molten mixtures of the type MeX2-MX (X = Cl, Br, I) have provided means of identifying and characterizing the species that may exist in the mixture and have information regarding the liquid structure of the MeX2 component. 

During the last decades of the twentieth century, a substantial development of experimental and especially, computational techniques took place. Thus, new measurement methods and mathematical processing of data appeared. This new information is not given anywhere in a comprehensive form and therefore, a lot of people working in this field are not acquainted with it. This book thus fills a substantial gap in this field of science. The book also documents the latest research in molten salt chemistry and brings new results and new insights into the study of molten salt systems using the results of X-ray diffraction and XSAF methods, Raman spectroscopy, and NMR measurements. 

Giakoumelou, L, Caraba, R., PSrvulescu, V., et al. (2002). First In Situ Raman Study of Vanadium Oxide Based SO2 Oxidation Supported Molten Salt Catalysts, Cattd. Letters, 78, pp. 209-214. 

The method of vibrational spectroscopy has found useful application to groups such as the NOg" ion< but studies of such entities as NiClf" or PtCll" by the laser Raman technique are still awaited. While NMR, ESR, and magnetic susceptibility studies of molten salt systems have been made, only the last have been of much use in coordination assignment. The techniques used to measure stability constants of complexes, such as polarography, potentiometry, and chromatography, are beginning to be applied to molten salt systems but the results to date require caution in interpretation. 

The Raman spectroscopy of fused systems should gain more prominence in the next few years, because of the interest in the molten state of ionic salts. Woodward has studied gallium dichloride by Raman spectroscopy, and concluded that the compound has the same form as in an aqueous solution and can be formulated as[Ga ] [GaCh ]. The Raman spectra of fused NaNOa, NaAsOs, and... 

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