Coordination of ions in aqueous solutions of erbium chloride from X-ray diffraction data

Aqueous solutions of erbium chloride were studied by X-ray diffraction over a broad range of concentrations under standard conditions. The prepeaks observed in the experimental scattering intensity curves were interpreted. The solutions were found to possess two types of structures. Saturated and concentrated solutions down to molar ratio of 1 : 20 have a quasi-crystalline structure defined by inter-ion interactions. Dilute solutions form a water-like structure characterized by a tetrahedral network of hydrogen bonds between water molecules. It was found that prepeaks can also be seen in the intensity curves of dilute solutions, which implies that these solutions retain the so-called long-range order.     

Coordination of ions in aqueous solutions of samarium chloride from X-ray diffraction data

The radial distribution functions for aqueous solutions of samarium chloride over a broad concentration range under standard conditions, obtained previously by X-ray diffraction, were used to develop various physically substantiated models for structural organization of the systems. The optimal versions were identified by calculating the theoretical functions for each model and comparing their agreement with experimental functions. The quantitative characteristics of the local environment of Sm³⁺ and Cl^– ions such as coordination numbers, interparticle distances, and sorts of ion pairs were established. The average number of water molecules in the first coordination sphere of the cation was found to decrease from 9 to 6 with increasing concentration. The structure of the systems is determined by solvent-separated ion associates over the whole concentration range.     

Structural parameters of the immediate environment of ions in saturated aqueous solutions of lanthanide chlorides,according to X-ray diffraction data

Saturated aqueous solutions of lanthanide chlorides are studied by means of X-ray diffraction. Models of the investigated solutions are used to calculate quantitative characteristics of the immediate environment of ions in solutions using the obtained experimental data. It is established that all of the investigated systems are characterized by similar structures. Cations coordinate six solvent molecules in the first coordination sphere as the Ln³⁺–OH₂ distances become shorter upon transitioning from light to heavy ions. Non-contact ion associates form in all the systems.     

Concentration dependence of the structure of aqueous solutions of samarium trichloride according to X-ray diffraction

Aqueous solutions of samarium chloride in a wide range of concentration under ambient conditions are studied by X-ray diffraction analysis. The small-angle peaks in experimental scattering intensity curves are interpreted. It is shown that highly concentrated solutions are characterized by a unique structure that differs heavily from the structure of dilute systems. It is found that small-angle peaks also appear in the intensity curves of dilute solutions, indicating that the so-called long-range order is preserved in these solutions. It is revealed that the contributions to the total scattering pattern that govern the appearance of prepeaks are interionic interactions of different types (e.g., cation-cation, anion-cation, and anion-anion interactions) in concentrated systems and the distances between the cations in dilute solutions.     

Concentration dependence of the structure of aqueous solutions of lutetium nitrate according to X-ray diffraction

Aqueous solutions of lutetium nitrate over a wide range of concentrations are studied by X-ray diffraction under standard temperature and pressure. The low-angle peaks in experimental scattering intensity curves are interpreted. It is shown that the structure of these solutions can be of two types. It is found that a saturated solution and solutions concentrated to a molar ratio of 1: 20 have a quasi-crystalline structure resulting from interionic interactions. It is determined that dilute solutions form a water-like structure characterized by a tetrahedral network of hydrogen bonds between the water molecules. It is found that low-angle peaks also appear in the intensity curves of dilute solutions; this proves that the so-called “long-range” order is preserved in these solutions. It is revealed that in all the studied systems, the contributions to the total scattering pattern that are responsible for the occurrence of pre-peaks are intercationic interactions.     

Composition and structure of pyrophoric nickel catalysts according to X-ray diffraction data

The properties of a nickel catalyst obtained by treatment of nickel–aluminum alloy with sodium hydroxide in the presence of H₂O₂ and additionally stabilized with increased pressure were studied. Additional stabilization decreased the catalyst activity by 25%, but gave a more distinct picture for an XRD analysis of the active catalyst surface and decreased the time of deactivation of the dehydrated catalyst with air oxygen. The catalyst stabilization was explained by the displacement of water, decrease in the pore size, and surface inhomogeneity.     

An X-ray diffraction study of aqueous solutions of lutetium trichloride

The X-ray diffraction analysis is used to study aqueous solutions of lutetium chloride in a wide concentration range under standard conditions. Small angle peaks on the functions of the X-ray scattering intensity and the maxima of radial distribution functions of the atomic-electron density are interpreted. It is found that highly concentrated solutions are characterized by a unique quasi-crystalline structure distinguished by short- and long-range ordering. Dilution of solutions results in that the own structure of the solvent starts to play the major role in the structure of the systems. It is established for the first time that small angle peaks on the scattering intensity functions are also manifested for diluted solutions, which indicates that long-range ordering is preserved in them.     

Microheterogeneous structure of aqueous solutions of nonelectrolytes X-ray diffraction studies

Journal of Structural Chemistry -     

Structure of aqueous sodium metaborate solutions: X-ray diffraction study

A structural analysis of aqueous sodium metaborate solutions (NaBo₂ · nH₂O, n = 10, 15, 20) at 298 ± 0.5 K by a rapid liquid ??-?? X-ray diffractometry with a highly effective X??celerator detector is reported in present paper. The radial distribution functions (RDF) and theoretical partial radial distribution functions for B-O, O-O, Na-O, Na-B, and Na-Na atom pairs were obtained from precisely diffraction data processing. Structure of aqueous sodium metaborate solutions was given through model calculation and described in three different items: hydrated sodium ion, hydrated metaborate ion and ion association. Effects of concentration on the structure of the solutions were discussed in detail. The mechanisms of ion aggregation and the formation of crystal nuclei in the solution are proposed. The results show that a clear picture of the structure of aqueous sodium metaborate solution has been acquired.     

The electrochemistry of gold in acid aqueous solutions containing chloride ions

Results obtained with differently prepared gold electrodes in acid solutions containing chloride ion at temperatures ranging from 22 to 65°C are reported. Potentiostatic techniques and rotating disc electrodes were employed. The anodic dissolution, the onset of passivity and the cathodic deposition of the metal are investigated under different experimental conditions. The anodic dissolution of Au is discussed in terms of possible reaction mechanisms involving the participation of different adsorbed species. The onset of passivation is related to the depletion of chloride ion at the reaction interface. The experimental voltammograms can be reporduced by means of an equation which considers the diffusion of chloride ion, the activation polarization related to the dissolution of Au and the establishment of passivity.     

Conformational characteristics of polyethylene glycol macromolecules in aqueous solutions according to refractometry data

The aqueous solutions of polyethylene glycols with molecular masses of 600, 1000, 1500, 3000, 6000, and 20000 were studied by refractometry. The conformational polarizabilities, mean-square distances between the ends of the macromolecular chain, segment lengths, and the number of Kuhn segments in a macromolecule were determined using the Lorentz-Lorentz equation. The polarizability of a hydrated macro-molecule was represented as the sum of polarizabilities of the nonhydrated macromolecule with retained conformation and polarizabilities of the water molecules involved in hydration of macromolecules. The size of macromolecules stabilized starting from a certain concentration. It was concluded that the initial concentration of stabilization shifts toward low concentrations as the molecular mass of polyethylene glycol increases. The dependence of the mean-square distance between the ends of the macromolecular chain on the number of Kuhn segments was expressed as the exponential function with index 0.3.     

Effect of concentration on the structure of aqueous solutions of gadolinium chloride and gadolinium nitrate as probed by X-ray diffraction

Aqueous solutions of gadolinium chloride and gadolinium nitrate are studied by X-ray diffraction over wide ranges of concentrations under standard temperature and pressure. Small-angle peaks on measured scattering intensity curves are interpreted. Small-angle peaks are found not only on the intensity curves for concentrated solutions, but also on those for dilute systems, and this proves that these systems retain a long-range order. Diverse types of ion-ion interactions are shown to be the major contributors to the overall scattering pattern that are responsible for the appearance of pre-peaks.