A New Predictive Equation for the Surface Tensions of Aqueous Mixed Ionic Solutions Conforming to the Linear Isopiestic Relation

The linear isopiestic relation has been used, together with the fundamental Butler equations, to establish a new simple predictive equation for the surface tensions of the mixed ionic solutions. This newly proposed equation can provide the surface tensions of multicomponent solutions using only the data of the corresponding binary subsystems of equal water activity. No binary interaction parameters are required. The predictive capability of the equation has been tested by comparing with the experimental data of the surface tensions for the systems HCl–LiCl–H₂O, HCl–NaClO₄–H₂O, HCl–CaCl₂–H₂O, HCl–SrCl₂–H₂O, HCl–BaCl₂–H₂O, LiCl–NaCl–H₂O, LiCl–KCl–H₂O, NaCl–KCl–H₂O, KNO₃–NH₄NO₃–H₂O, and LiCl–NaCl–KCl–H₂O at 298.15 K; KNO₃–NH₄Cl–H₂O, KBr–Sr(NO₃)₂–H₂O, NaNO₃–Sr(NO₃)₂–H₂O, NaNO₃ –(NH₄)₂SO₄–H₂O, KNO₃–Sr(NO₃)₂– H₂O, NH₄Cl–Sr(NO₃)₂–H₂O, NH₄Cl– (NH₄)₂SO₄–H₂O, KBr–KCl–H₂O, KBr–KCl–NH₄Cl–H₂O, KBr–KNO₃– Sr(NO₃)₂–H₂O, KBr–NH₄Cl–Sr(NO₃)₂–H₂O, KNO₃–NH₄Cl–Sr(NO₃)₂–H₂O, and NH₄Cl–(NH₄)₂SO₄–NaNO₃–H₂O at 291.15 K; and KBr–NaBr–H₂O at temperatures from 283.15 to 308.15 K. The agreement is generally quite good.     

Zirconium-Containing Compositions with a Component Ratio Characteristic of the Garnet Structure: Physicochemical and Catalytic Properties

The possibility for the formation of garnet structures in the Mn–Fe–Zr–O and Ca–Sm–Zr–O systems obtained by the precipitation of the corresponding salts is studied. It is shown that, in the Mn–Fe–Zr–O system, garnet is crystallized at 860–920°C, for which probable cation distribution is estimated to be {Zr_2.5 ⁴⁺Mn_0.5 ²⁺}[Mn₂ ²⁺](Fe_2.5 ³⁺Mn_0.5 ³⁺)O₁₂. In the Ca–Sm–Zr–O system, the perovskite CaZrO₃, pyrochlore Sm₂Zr₂O₇, and CaO are formed at 900–1200°C, but compounds with garnet structures are not found. The reported systems are characterized by surface areas of 300–450 m²/g at 450°C, and they have the polydisperse distribution of pores over sizes. The introduction of surfactants at the stage of component mixing enables an increase in the overall pore volume and mechanical strength of these systems. The Mn–Fe–Zr and Ca–Sm–Zr compositions are active catalysts for the complete oxidation of hydrocarbons.     

Extraction characteristics of pertechnetate with tetraphenylarsonium in the presence of chloride,nitrate and perchlorate anions

Selected extraction systems of TcO ₄ ^– –(H,Na)A–H₂O/R(TcO₄,A)–CHCl₃, C₆H₅NO₂ type, where A=Cl^–, NO ₃ ^– , ClO ₄ ^– , R=(C₆H₅)₄As⁺, were studied. The solvent extraction of sub- and super-stoichiometric ratio of TcR was performed. The solubility of (C₆H₅)₄AsTcO₄ in water, chloroform and nitrobenzene were determined too. The results of the extractions are presented in the form of TcO ₄ ^– distribution dependencies on the phase composition and the extraction constants of individual TcO ₄ ^– , Cl^–, NO ₃ ^– , ClO ₄ ^– anions and TcO ₄ ^– -Cl^–, TcO ₄ ^– –NO ₃ ^– , TcO ₄ ^– –ClO ₄ ^– ion pairs.     

Enthalpies of formation of some phases present in the Y−Ba−Cu−O system by solution calorimetry

Enthalpies of some of the phases in the Y–Ba–Cu–O system were determined by solution calorimetry using a Calvet microcalorimeter. The standard enthalpies of formation for the phases were found to be YBa₂Cu₃O_6.60, –2627.9; YBa₂Cu₃O_6.77, –2641.8; YBa₂Cu₃O_6.90, –2652.0; YBa₂Cu₃O_6.99, –2659.3; Y₂Cu₂O₅, –2198.6; Y₂BaCuO₅, –2656.4; BaCuO_2.33, –788.6; and BaCuO_2.42, –796.2 kJ-mol^–1.     

Spectroscopic study of vinylidene chloride—Vinyl chloride copolymers

Summary Deuteration technique was applied to study the micro structures of copolymer series VDC/VC by infrared spectroscopy and high resolution NMR. The CH₂ bending modes of chlorine atom containing polymers assigned as follows; –CCl₂CH₂CCl₂– 1405 cm^–1 (cryst.) and 1410 cm^–1 (amorph.), –CHClCH₂CCl₂– 1422 cm^–1, –CHClCH₂CHCl– 1428 cm^–1 (cryst.) and 1432 cm^–1 (amorph.) –CHClCH₂CH₂CHCl– 1445 cm^–1 and –CCl₂CH₂CH₂CCl₂– 1448 cm^–1. This infrared interpretation shows that only the head to tail addition occurs in the copolymerisation. Nine peaks of the methylene protons were observed clearly in the NMR spectra of the copolymers. The study of the deuterated copolymers revealed that the effects of the chemical groups until the third at both sides from the marked methylene and the stereo configuration of long VC part should be considered to assign the NMR spectra. The CCl₂ group made the chemical shift of the methylene proton to appear at lower magnetic field and the CHCl group gave the opposite behavior.

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Zusammenfassung Mit deuterierten Monomeren wurde die Mikrostruktur der Copolymerenserie Vinyliden-Chlorid/Vinyl-Chlorid im Infraroten und mit hochauflösender Kernresonanz untersucht. Für die Biegeschwingung der Chloratome enthaltenden Polymeren der Methylengruppe ergeben sich folgende Werte: –CCl₂CH₂CCl₂– 1405 cm^–1 (krist.) und 1410 cm^–1 (amorph.), –CHClCH₂CCl₂– 1422 cm^–1, –CHClCH₂CHCl– 1428 cm^–1 (krist.) und 1432 cm^–1 (amorph.), –CHClCH₂CH₂CHCl– 1445 cm^–1 und –CCl₂CH₂CH₂CCl₂– 1448 cm^–1.Diese Interpretation des Infraroten zeigt, daß nur die Kopf-Schwanz-Addition bei der Copolymerisation stattfindet. Neun Maxima des Methylenprotons wurden deutlich in den NMR-Spektren der Copolymeren beobachtet. Die Untersuchungen an den deuterierten Copolymeren zeigen, daß die Effekte der chemischen Gruppen bis zur dritten nach beiden Seiten vom markierten Methylen und die Stereokonfiguration von langen Vinyl-Chlorid-Anteilen betrachtet werden müssen, um die NMR-Spektren zu beschreiben. Die CCl₂-Gruppe läßt die chemische Verschiebung des Methylen-protons bei geringeren magnetischen Feldern und die CHCl-Gruppe bei höheren erscheinen.

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With 5 figures in 13 details and 4 tables     

Determination of oxygen in fluoride glass by proton activation analysis

Oxygen was determined in three kinds of ZrF₄-based fluoride glass [ZrF₄–BaF₂–GdF₃–AlF₃ (ZBGA), ZrF₄–BaF₂–LaF₃–YF₃–AlF₃–LiF–NaF (ZBLYALN) and ZrF₄–BaF₂–LaF₃–YF₃–AlF₃–LiF (ZBLYAL)] used for fabricating optical fiberby¹⁸O(p, n)¹⁸F reaction without significant nuclear interference. The main long life⁹⁶Nb nuclide was produced by the⁹⁶Zr(p,n) reaction in a non-destructive analysis of ZBGA-fluoride glass and reduced by using a coincidence system with Ge(Li) and NaI(T1) detectors. Substoichiometric separation of¹⁸F was also used to determine oxygen in fluoride glass, especially in glass containing yttrium as a component element because the⁸⁹Zr produced by the⁸⁹Y(p,n) reaction is a positron emitter, the same as¹⁸F. It was confirmed that the oxygen concentration in fluoride glass was 13–2460 ppm related to the loss by scattering.     

Geochemical and gamma spectrometric analysis of ores and hostrocks of the Kanawa uranium occurrence in NE Nigeria

The Kanawa mineralization is one of the numerous low grade U-occurrences in the Gubrunde horst, NE Nigeria. Eighty nine samples consisting of ore and host rocks have been analyzed for 12 elements and 3 isotopes by atomic absorption spectrometry, colorimetry and direct -spectrometric methods and the data described using multivariate statistical techniques. The results show an enhancement of U, Mn, P₂O₅, Fe₂O₃, CaO,²¹⁰Pb,²²⁶Ra and²³⁴Th in the ore zones. The element/isotopic associations (U–P₂O₅–²¹⁰Pb–²²⁶Ra–²³⁴Th), (Na₂O–K₂O–MgO), (Fe₂O₃–MnO–CaO–Cu) were established in the mineralized rhyolites, while (P₂O₅–²¹⁰Pb–²²⁶Ra–²³⁴Th), (Na₂O–K₂O–MgO–Zn) and Fe₂O₃–Mn–U) occur in the altered/unmineralized rocks. The variation in the pattern of association of Cu, U, Zn and CaO could be ascribed to their remobilization, depletion, enrichment or introduction in the ore zone by hydrothermal solutions. The elements/isotopes U, Zn, Cu, P₂O₅,²²⁶Ra,²¹⁰Pb,²³⁴Th or their ratios could in addition to Pb, Ba, Ce, Sm be used as pathfinder elements in prospecting concealed ores in NE Nigeria.     

ZnO nanorods decorated calcined Mg–Al layered double hydroxides as photocatalysts with a high adsorptive capacity

The nanocomposites of magnesium–aluminium–carbonate–layered double hydroxides (Mg–Al–CO₃–LDHs) and ZnO nanorods were prepared via a homogeneous precipitation process. The presence of ZnO nanorods made the calcined Mg–Al–CO₃–LDHs, the strong adsorptive adsorbents for anions, have a photocatalytic activity. Both Mg–Al–CO₃–LDHs and the nanocomposites with various ZnO/Mg–Al–CO₃–LDHs mass ratios from 0.5:1 to 3:1 were characterized by X-ray diffraction, transmission electron microscope and UV–vis diffuse reflectance spectra. The nanocomposites quickly adsorbed the anionic dyes such as acid red G (ARG) without the light illumination, and the adsorbed dyes on the recovered nanocomposites were then degraded in a separated photocatalytic reactor. The adsorption ability of the nanocomposites and their photocatalytic activities for the removal of ARG were evaluated by the Fourier transform infrared spectra and UV–vis extinction spectra. The sample at 3:1 ZnO/Mg–Al–CO₃–LDHs mass ratio was shown to have higher photocatalytic efficiencies.     

Quantitative chemical analysis on paper: Determination of phosphate in the presence of large quantities of other ions

Summary A rapid method has been developed for the determination of phosphate by means of filter paper impregnated with lead iodide. A sample is added to the impregnated filter paper by means of a capillary, and after irrigation to cause migration of the ions a white spot is obtained as the lead iodide is converted into the phosphate. The weight of the spot is dependent on the p_H and the quantity of phosphate present.The determination is possible in the presence of SCN^–, Cl^–, Br^–, NO₃ ^–, CO₃ ^–, I^–, IO₃ ^–, CH₃COO^–, B₄O₇ ^2–, F^–, Sb₂O₇ ^4–, K⁺, Na⁺, NH₄ ⁺, OH^–, H⁺, succinic, citric and tartaric acids. The determination is impossible in the presence of C₂O₄ ^2–, SO₄ ^2–, MoO₄ ^2–, NO₂ ^–, SO₃ ^2–, S^2–, CrO₄ ^2–, or CO₃ ^2–.The method permits the determination of 7–100g of phosphate with an accuracy of 2%.

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Zusammenfassung Ein schnelles Verfahren zur Phosphatbestimmung wird besehrieben, bei dem man sich eines mit Bleijodid imprägnierten Filterpapiers bedient. Die Probe wird mit einer Kapillare auf das Papier aufgebracht. Man erleichtert die Ionenbewegung durch geeignete Befeuchtung und erhält einen weißen Fleck infolge Umsetzung des Bleijodids in -phosphat. Das Gewicht des Fleckens hängt vom p_H und von der Phosphatmenge ab.Die Bestimmung ist möglich in Gegenwart von SCN^–, Cl^–, Br^–, NO₃ ^–, CO₃ ^–, J^–, JO₃ ^–, CH₃COO^–, B₄O₇ ^2–, F^–, Sb₂O₇ ^4–, K⁺, Na⁺, NH₄ ⁺, OH^–, H⁺, Bernsteinsäure, Zitronensäure und Weinsäure; sie ist nicht möglich bei Gegenwart von C₂O₄ ^2–, SO₄ ^2–, MoO₄ ^2–, NO₂ ^–, SO₃ ^2–, S^2–, CrO₄ ^2– oder CO₃ ^2–. 7 bis 100g Phosphat können mit einer Genauigkeit von 2% bestimmt werden.

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Résumé On a développé une méthode rapide pour le dosage des phosphates sur papier-filtre imprégné d'iodure de plomb. On dépose l'échantillon sur le papier-filtre imprégné, à l'aide d'un capillaire, et, après humidification pour provoquer la migration des ions, on obtient une tache blanche quand l'iodure de plomb est converti en phosphate. Le poids de la tache dépend du p_H et de la quantité de phosphate présent.Le dosage est possible en présence de SCN^–, Cl^–, Br^–, NO₃ ^–, CO₃ ^–, I^–, IO₃ ^–, CH₃COO^–, B₄O₇ ^2–, F^–, Sb₂O₇ ^4–, K⁺, Na⁺, NH₄ ⁺, OH^–, H⁺, et des acides succinique, citrique et tartrique. Il est impossible en présence de C₂O₄ ^2–, SO₄ ^2–, MoO₄ ^2–, NO₂ ^–, SO₃ ^2–, S^2–, CrO₄ ^2– ou CO₃ ^2–.La méthode permet le dosage de 7 à 100g de phosphate avec une précision de 2%.

     

Cu-superconductors in organic catalysis, II. The conversion of benzyl alcohol on various Cu-catalysts

The catalytic conversion of benzyl alcohol to toluene and benzaldehyde was performed on YBa₂Cu₃O_7–x (Y–Ba–Cu–O) in the presence of hydrogen at 250–400°C. The catalytic characteristics of Y–Ba–Cu–O were compared with those of CuO, Cu/SiO₂ and Y₂BaCuO₅. The structural changes in the catalysts during the reaction were measured by means of XRD and SEM. It was found that the oxidation state of the copper in Y–Ba–Cu–O was a considerable factor in the conversion of benzyl alcohol.Part I:React. Kinet. Catal. Lett. 51, 61 (1993).     

Synthesis and Structure of Organoantimony Peroxides

Organoantimony peroxides (Ar₂SbO)₄(O₂)₂ (Ar = Ph, p-Tol) were synthesized by oxidation of triarylantimony with hydrogen peroxide in the presence of nitrosophenol or 4-chlorophenol in an ether solution. X-ray diffraction analysis of peroxides obtained revealed that four antimony atoms have octahedral coordination and are connected via bridging oxygen atoms and two peroxide groups. The C–Sb, Sb–O_br, Sb–OO, and O–O distances are equal to 2.106–2.127, 1.958–1.974, 2.202–2.246, 1.471, 1.470 Å (Ar = Ph) and 2.086–2.139, 1.932–1.983, 2.215–2.289, 1.445–1.466 Å (Ar = p-Tol).     

Quantum Chemical Calculation of Conformations and Rotation Barriers of Functional Groups in Arylsulfonyl Halides

The semiempirical PM3 method is used to calculate the potential functions of internal rotation of the functional groups –SO₂Cl, –NO₂, –CH₃, –OCH₃, and –NH₂ of benzenesulfonyl halide molecules (PhSO₂Hal, Hal = F, Cl, Br, I) and twelve substituted derivatives of benzenesulfonyl chloride. Molecular conformations have been determined and internal rotation barriers of the functional groups have been calculated. For meta- and para-substituted benzenesulfonyl chlorides, the projection of the S–Hal bond is perpendicular to the plane of the benzene ring. The rotation barriers of the –SO₂Hal group of benzenesulfonyl halides increase in the series Hal = F, Cl, Br, I. The rotation barriers of the –SO₂Cl group of benzenesulfonyl chloride with meta- and para-substituents slightly increase with the electron-donor properties of the substituent. The rotation barriers of the functional groups of ortho-substituted benzenesulfonyl chlorides are 3 or 4 times as high as those of the meta- and para-isomers. For para-substituted benzenesulfonyl chlorides, the rotation barriers of the functional groups increase in the order –CH₃, –NO₂, –SO₂Cl, –OCH₃, –NH₂.     

In situ study on the effects of Ni and Mo on the passive film formed on Fe–20Cr alloys by photoelectrochemical and Mott–Schottky techniques

Effects of alloying elements (Ni and Mo) on the structure of passive film formed on Fe–20Cr alloys in pH 8.5 buffer solution were explored by analyzing the in situ electronic properties measured using the photoelectrochemical technique and Mott–Schottky analysis. The passive film formed on Fe–20Cr–10Ni was found to be mainly composed of Cr-substituted γ-Fe₂O₃ from similarities in photocurrent response for the passive films formed on the alloy and Fe–20Cr. On the other hand, the photocurrent spectra for the passive films of Fe–20Cr–15Ni–(0, 4)Mo alloys exhibited the spectral components associated with NiO and Mo oxide (MoO₂ and/or MoO₃) in addition to that induced by Cr-substituted γ-Fe₂O₃. Mott–Schottky plots for the passive films formed on Fe–20Cr–(10, 15)Ni and Fe–20Cr–15Ni–4Mo confirmed that the passive films on Fe–20Cr–(10, 15)Ni–(0, 4)Mo alloys have a base structure of Cr-substituted γ-Fe₂O₃ with variation of densities of shallow and deep donors depending on the Ni and Mo contents in the alloys. We suggest that the passive film formed on Fe–20Cr–(10, 15)Ni and Fe–20Cr–15Ni–4Mo alloys are composed of (Cr, Ni, Mo)-substituted γ-Fe₂O₃ when the concentrations of Ni and Mo are below critical values. However, NiO and Mo oxide (MoO₂ and/or MoO₃) would be precipitated in the passive films when the concentrations of Ni and Mo exceed critical values.     

Reactions of organylhalosilanes with 1,1,3,3-tetra- and hexamethyldisilazane

Organylchlorosilanes, and also SiCl₄, decompose 1,1,3,3-tetra- and hexamethyl-disilazanes with formation of hitherto unknown organylchlorosilazanes of general formulas R_4–nSiCl_n–1NHSiH(CH₃)₂ and R_4–nSiCl_n–1NHSi(CH₃)₃ (n=2–4) in yields of 54–98%. The IR and mass spectra of the prepared compounds were studied.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1159–1162, May, 1991.     

A Laboratory Investigation of the Reduction of Chromium Oxide by a Reverse-Polarity DC Plasma-Driven Molten Oxide Electrolysis Process

A method for producing chromium metal/chromium alloys using a reverse-polarity DC plasma-driven molten oxide electrolysis process was investigated. A laboratory-scale 50 kW DC plasma-crucible system was designed and built to investigate the feasibility of this process. Experiments on molten oxide electrolysis were successfully conducted to produce chromium metal from chromic oxide. Two starting slag systems, SiO₂–CaO–Al₂O₃–Cr₂O₃–Na₂O and SiO₂–CaO–Cr₂O₃–Na₂O, were used in this study. It was found that in each case chromic oxide was successfully reduced to metallic chromium. Aluminum was also reduced with the presence of alumina in the starting slag. Small amounts of carbon monoxide gas were introduced to the electrolysis system to study oxygen evolution rates from the plasma/slag interface. For the SiO₂–CaO–Al₂O₃–Cr₂O₃–Na₂O system, the oxygen evolution rate showed a maximum during the electrolysis process. For the SiO₂–CaO–Cr₂O₃–Na₂O system, the oxygen evolution rates displayed a declining trend with processing time. These two reduction behaviors were apparently controlled by different mechanisms. The significance of this process is that it might be used to produce carbon-free chromium metal/chromium alloys without carbon containing reducing agent and since no carbon based reactants are used for heating or reduction there are no carbon dioxide emissions.     

Thermodynamics of aqueous mixtures of sodium chloride,potassium chloride,sodium sulfate,and potassium sulfate at 25°C

Aqueous solutions of sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate can be mixed in six ways to give ternary mixtures. Two of these have already been studied and results are now presented for the remaining four systems: H₂O–NaCl–K₂SO₄, H₂O–Na₂SO₄–K₂SO₄, H₂O–KCl–Na₂SO₄, and H₂O–KCl–K₂SO₄.     

Kinetics and mechanism of formation of tetrachloropalladate(II) in the reactions of bis(oxalato)- and bis(malonato) palladate(II) with chloride in acid media

Summary Kinetics of formation of [PdCl₄]^2– from [Pd(ox)₂]^2– and [Pd(mal)₂]^2– has been studies in aqueous acid media in the presence of an excess of chloride ion by stopped-flow spectrophotometry. Both the complexes undergo the transformation in two well separated consecutive steps. In 0.02–0.05 M acid with 0.2 M Cl^–, Pd(AA)^2– dissociates leading to the formation of [Pd(AA)Cl₂]^2– (where AA =ox^2– or mal^2–), which in 0.1–0.6 M acid and 1 M Cl^– forms [PdCl₄]^2– in a relatively slow step. For both steps k_abs=k₀+k₂[H⁺][Cl^–]. Activation parameters corresponding to k₀ and k₂ have been determined. Results indicate that [Pd(mal)₂]^2– is much more labile to substitution than [Pd(ox)₂]^2– and for both the lability is far greater than that of [Pd(bigH)₂]²⁺ and [Pt(ox)₂]^2– reported earlier.     

Influence of Anions on Electrochemical Properties of Polypyrrole-Modified Electrodes

The influence of anions ClO₄ ^–, NO₃ ^–, Cl^–, SO₄ ^2–, and DDS^– (dodecyl sulfate) on the cyclic voltammetric response of polypyrrole-modified electrodes is studied. The change in the film composition is examined by electron probe microanalysis. It is established that essential changes in the shape of voltammograms take place during cycling if the anions are not sufficiently freely mobile in the polymer film and insertion of cations from the solution is necessary to guarantee electroneutrality of the system. Some differences between the mobility of Cl^– ions and ClO₄ ^– or NO₃ ^– ions are in good agreement with the results of semi-empirical quantum chemical calculations showing that the interaction of Cl^– and Br^– ions with pyrrole oligomers is stronger than that of NO₃ ^– or ClO₄ ^– ions. Nevertheless, it is established that the peak current determined from voltammograms increases linearly with the increase of the scan rate with very high correlation coefficient. It means that it is possible to describe the behavior of ClO₄ ^–, NO₃ ^– and Cl^– ions in the framework of the model of free ions. The redox behavior of the PPy films doped with anions of low mobility such as SO₄ ^2– and DDS^– depends essentially on the nature of cations in the test solution. It is found that the mobility of cations increases in the row Li⁺ < Na⁺ < K⁺ < Cs⁺. The mobility of DDS^– ions in the PPy in ethanolic solution is significantly higher and their electrochemical properties are quite similar to PPy|Cl or NO₃ ^– film in aqueous solution.     

Effect of the Conditions of Thermal Treatment of Molybdenum–Titanium and Vanadium–Molybdenum–Titanium Oxide Catalysts on Pore Structure Formation

The effect of the conditions of thermal treatment on the texture formation in molybdenum–titanium oxide (Mo–Ti–O) and vanadium–molybdenum–titanium oxide (V–Mo–Ti–O) catalysts was studied. It was found that the presence of MoO₃ in the Mo–Ti–O catalyst resulted in the stabilization of the surface area of anatase and in the retention of the fine pore structure upon thermal treatment because of the insertion of highly dispersed molybdenum crystallites into the aggregates of anatase crystallites, preventing from their agglomeration over a wide range of temperatures. In the presence of MoO₃ and V₂O₅ in the catalyst, anatase particles underwent agglomeration as the temperature was increased. This resulted in a more drastic decrease in the specific surface area and an increase in the pore size, as compared with binary samples, because of the formation of a thermally labile vanadium–molybdenum compound at the surface of anatase.     

Water in melts: Raman spectral investigation of the molten Ca(NO3)2·4H2O−KNO3 system

The Raman spectra of molten mixtures of Ca(NO₃)₂\4H₂O–KNO₃ have been examined, covering the concentration range of 0–70 mole% KNO₃. The frequencies in the spectra of the mixtures have been found to change slightly with concentration. Striking variations in the band shapes have been observed in the regions corresponding to the O–H stretching mode (2850–3850 cm^–1) and the v₄-NO ₃ ^– mode (700–750 cm^–). The results are discussed in terms of perturbed quasi-lattice structure for the melt, in which there could be a displacement of water molecules in the first coordination sphere around Ca²⁺ by the NO ₃ ^– ion.