Metastable Equilibrium in Quaternary System Li2SO4 ＋ K2SO4＋Li2CO3 ＋ K2CO3 ＋ H2O at 288 K

IntroductionThe Zhabuye salt lake, Tibet in China, is famousfor the high concentrations of lithium, boron, andpotassium in the world. The main components areLi , K , Na , B4O72 -, CO32 -, Cl-, SO42 -, andH2O, including rare elements such as Rb and Cs .The…     

五元体系Li＋, K＋//, CO32- ,SO42- , B4O72- -H2O在288 K时的介稳相平衡研究

采用等温蒸发法研究了五元体系Li^＋, K^＋//, , -H₂O 在288 K时的介稳相平衡关系, 测定了该五元体系在288 K条件下的介稳平衡的溶解度和溶液密度, 根据实验数据绘制了相应的介稳平衡相图和水图. 相平衡研究结果表明该五元体系介稳相平衡中有复盐K₂SO₄•Li₂SO₄生成, 其介稳相图(Li₂CO₃饱和)有4个共饱和点, 9条单变量曲线, 6个Li₂CO₃饱和的结晶区分别为LiBO₂•8H₂O, K₂B₄O₇•4H₂O, K₂CO₃•3/2H₂O, K₂SO₄, Li₂SO₄•H₂O和复盐 K₂SO₄•Li₂SO₄.     

五元体系Li~+,K~+//CO_3~(2-),SO_4~(2-),B_4O_7~(2-) -H_2O在288 K时的介稳相平衡研究

采用等温蒸发法研究了五元体系Li~+,K~+//CO_3~(2-),SO_4~(2-),B_4O_7~(2-) -H_2O在288 K时的介稳相平衡关系,测定了该五元体系在288 K条件下的介稳平衡的溶解度和溶液密度,根据实验数据绘制了相应的介稳平衡相图和水图,相平衡研究结果表明该五元体系介稳相平衡中有复盐K_2SO_4·Li_2SO_4生成,其介稳相图(Li_2CO_3饱和)有4个共饱和点,9条单变量曲线,6个Li_2CO_3饱和的结晶区分别为LiBO_2·8H_2O,K_28_4O_7·4H_2O,K_2CO_3·3/2H_2O,K_2SO_4,Li_2SO_4·H_2O和复盐K_2SO_4·Li_2SO_4.     

K2B4O7-Na2B4O7-Li2B4O7-H2O 四元体系15℃介稳相平衡研究

采用等温蒸发平衡法研究了四元体系K2B4O7-Na2B4O7-Li2B4O7-H2O15℃时的介稳相平衡及平衡液相的物化性质(密度,粘度,电导率,折光率,pH)。根据实验数据绘制了相图,相图中有一个共饱点E,三条单变度曲线E3F,E2F,E1F;三个平衡固相分别为：K2B4O7•4H2O,Na2B4O7•10H2O和Li2B2O4•16H2O;硼酸钾具有最大溶解度,硼酸钠具有最小溶解度。同时,根据试验数据绘制了组成－物化性质关系图,从图可见溶液的密度,粘度和折光率均随着溶液浓度的增大而逐渐增大,在共饱和点F处达到最大值,而溶液的pH值和电导率却随着溶液浓度的增大呈总体下降的趋势。     

K2B4O7-Na2B4O7-Li2B4O7-H2O四元体系273 K介稳相平衡

采用等温蒸发平衡法研究了四元体系K2B4O7-Na2B4O7-Li2B4O7-H2O在273 K时的介稳相平衡及平衡液相的密度. 研究发现该四元体系为简单共饱和型, 无复盐及固溶体形成, 根据溶解度数据绘制了相图, 相图中有一个共饱点E, 三条单变度曲线E3E, E2E, E1E; 三个平衡固相分别为K2B4O7·4H2O、Na2B4O7·10H2O 和LiBO2·8H2O. 并简要讨论了实验结果.     

Phase polymorphism of [Ni(DMSO)6](BF4)2 studied by differential scanning calorimetry

The tetrafluoroborate of hexadimethylsulfoxidenickel(II) was synthesized and studied by differential scanning calorimetry. Seven solid phases of [Ni(DMSO)₆](BF₄)₂ were revealed. Specifically, six phase transitions of the first order were detected between the following solid phases: stable KIb → stable KIa at T _C6 = 335 K, metastable KIIb → metastable KIIa at T _C5 = 368 K, metastable KIII → overcooled phase KI at T _C4 = 378 K, metastable KIIa → overcooled phase KI at T _C3 = 396 K, stable KIa → stable KI at T _C2 = 415 K and stable KI → stable K0 at T _C1 = 433 K. [Ni(DMSO)₆](BF₄)₂ begins decomposition at 440 K with loss of one DMSO molecule per formula unit forming [Ni(DMSO)₅](BF₄)₂ (phase L0) which melts next in two steps in the temperature range 550–593 K. From the entropy changes connected both with melting and with phase transitions, it can be concluded that phases KI, overcooled KI and K0 are orientationally dynamically disordered (ODIC) crystals. Stable phases KIb, KIa and metastable phase KIII are ordered solid phases. Metastable phase KIIa and metastable phase KIIb are more or less ordered solid phases.     

Li＋, Na＋//SO42－, CO32－-H2O交互四元体系288 K介稳相平衡研究

采用等温蒸发法研究了四元体系Li^＋, Na^＋// SO₄^2－, CO₃^2－-H₂O 288 K介稳相平衡及平衡液相的密度、电导率、折光率、粘度和pH值, 测定了该四元体系288 K条件下介稳平衡溶液溶解度及物化性质. 根据实验数据绘制了相应的介稳相图. 研究发现: 该体系介稳平衡中有复盐Na₃Li(SO₄)₂•6H₂O形成. 其介稳相图中有3个共饱点, 7条单变量曲线, 平衡固相为: Li₂SO₄•H₂O, Na₂SO₄, Na₃Li(SO₄)₂•6H₂O, Li₂CO₃, Na₂CO₃•10H₂O. 复盐Na₃Li(SO₄)₂•6H₂O和一水硫酸锂(Li₂SO₄•H₂O)的结晶区较小, 而Li₂CO₃的结晶区最大; 该四元体系介稳平衡条件下未发现Na₂SO₄•10H₂O的结晶区.     

Electron-impact-induced rearrangements of organic ions VIUnimolecular reactions of isomeric[C8H9]+ions

Metastable ion spectra and deuterium labelling have been used to investigate a series of gaseous [C₈H₉]+ ions of isomeric structures. The similarity of the intensities of their metastable loss of hydrogen, acetylene and ethylene molecules and metastable reactions of specifically labelled ions, suggests that the [C₈H₉]+ reacting ions, formed initially with different structures, isomerise to a common structure or mixture of structures via deep-seated rearrangement reactions which render all hydrogen atoms equivalent. The isomerisation process involved is controlled by a conversion of a vinyl bond into an allyl-type bond, thus destroying the aromatic moiety.     

Metastable Phase Equilibrium in the Aqueous Ternary System K<Subscript>2</Subscript>SO<Subscript>4</Subscript>+MgSO<Subscript>4</Subscript>+H<Subscript>2</Subscript>O at (288.15 and 308.15) K

The metastable solubilities and densities of the aqueous ternary system K₂SO₄+MgSO₄+H₂O at (288.15 and 308.15) K were determined with the isothermal evaporation method. Using the experimental results, the metastable phase diagram and the densities versus composition diagram were plotted. In the metastable phase diagrams of the ternary system at (288.15 and 308.15) K, there are in all two invariant points, three univariant solubility curves, and three metastable crystallization regions corresponding to arcanite (i.e., anhydrous potassium sulfate, K₂SO₄), picromerite (K₂SO₄⋅MgSO₄⋅6H₂O) and epsomite (MgSO₄⋅7H₂O) that are formed in the metastable equilibrium system. A comparison of the stable and metastable phase diagrams at each temperature shows that the metastable regions of magnesium sulfate are obvious, and the crystallizing regions of epsomite and arcanite are much larger than those in the stable phase diagram. The densities of the system changed regularly with the magnesium sulfate content. The resulting information can be used to recover potassium or remove magnesium. The calculated densities using an empirical equation agree well with the experimental results.     

Effects of different temperatures and additives on the metastable zone width precipitation kinetics of NaBO2

In this study, the sodium metaborate, which is applicable in various industrial areas, and its metastable zone width that is very important for its production by crystallization, and its nucleation are investigated to obtain the necessary thermodynamic parameters. The polythermal and isothermal method has been used for the measurement of metastable zone width. Metastable zone width of NaBO₂ has found at 9°C at average and cooling rate do not have any effect on it. In addition, the effect of sodium metaborate on the hydrogen storage capacity of sodium borohyride solutions that is known as one of the best hydrogen sources today is investigated at the various concentrations of sodium borohyride in the medium. Results have shown that three different areas emerged as the percentage of NaBH4 in the solution increased.     

(Solid + liquid) metastable equilibria in quaternary system (Li2SO4 + K2SO4 + Li2B4O7 + K2B4O7 + H2O) at T = 288 K

Metastable equilibrium solubilities and properties such as densities, conductivity, pH, refractive index, and viscosity of the solution were determined experimentally. According to the experimental data, the metastable equilibrium phase diagram was plotted. In the phase diagram, there are three invariant points, seven univariant curves, five fields of crystallization: Li₂SO₄ · H₂O, K₂SO₄, Li₂B₄O₇ · 3H₂O, K₂B₄O₇ · 4H₂O, and K₂SO₄ · Li₂SO₄. The double salt K₂SO₄ · Li₂SO₄ was found in the quaternary system metastable equilibria. Lithium sulfate (Li₂SO₄) has the highest concentration and strong salting-out effects on other salts.Also, the relationship diagram between the properties and the ion concentration of solution was constructed. It can be seen from the relationship diagram that the equilibrium solution density values, viscosity values, and refractive index values are increased apparently with the rise of sulfate ion concentration, reaching the maximum values at eutonic point F3. Electrical conductivity values and pH values, however, fall down with the rise of ion concentration on the whole.     

13C labelling study of the interconversion of ethylbenzene, 7-methylcycloheptatriene and p-xylene ions

The isomerization of the molecular ions of ethylbenzene, 7-methylcycloheptatriene and p-xylene by skeletal rearrangement prior to the formation of [C₇H₇]⁺ ions has been investigated by using ¹³C labelled compounds. The results obtained for ions generated by 70 eV and 12 eV electron impact, and fragmenting in the ion source, the 1st field free region and the 2nd field free region, respectively, are compared with those obtained from D labelled derivatives. It is shown that at long reaction times metastable p-xylene ions lose a methyl radical after scrambling of all C atoms and H atoms, while the unstable molecular ions in the ion source react by specific loss of one of the methyl substituents. Both unstable and metastable ethylbenzene ions fragment by two competing mechanisms, one corresponding to specific loss of the terminal methyl group, and the other involving scrambling of all C and H atoms. These results are discussed by use of a dynamic model developed for the mutual interconversion and fragmentation of the molecular ions of ethylbenzene, methylcyclo-heptatriene and p-xylene. The experimental results can be explained by an equilibrium between metastable methylcycloheptatriene ions and p-xylene ions with sufficient energy for skeletal rearrangement, while about 40% of the metastable ethylbenzene ions fragment after rearrangement to methylcycloheptatriene ions and about 60% of the ethylbenzene ions rearrange further to xylene ions before fragmentation. Metastable methylcycloheptatriene ions, mainly lose a methyl group without a skeletal rearrangement, however, because the rearranged ions are kinetically trapped as ‘stable’ xylene ions or ethylbenzene ions.     

Metastable States of small-molecule solutions

Metastable states such as gels and glasses that are commonly seen in nanoparticle suspensions have found application in a wide range of products including toothpaste, hand cream, paints, and car tires. The equilibrium and metastable state behavior of nanoparticle suspensions are often described by simple fluid models where particles are treated as having hard cores and interacting with short-range attractions. Here we explore similar models to describe the presence of metastable states of small-molecule solutions. We have recently shown that the equilibrium solubilities of small hydrogen-bonding molecules and nanoparticles fall onto a corresponding-states solubility curve suggesting that with similar average strengths of attraction these molecules have similar solubilities. This observation implies that metastable states in small-molecule solutions may be found under conditions similar to those where metastable states are observed in nanoparticle and colloidal suspensions. Here we seek confirmation of this concept by exploring the existence of metastable states in solutions of small molecules.     

Thermodynamique des melanges binaires LiPO3-Pb(PO3)2: Diagramme de phases et étude thermodynamique du liquide

Study of solid-liquid phase diagram of LiPO₃-Pb(PO₃)₂ binary system, in certain calcination conditions, shows the existence of several metastable phasis. When heated at a temperature of 723 K the binary mixtures lead uncompletely to a defined compound Pb₂Li(PO₃). On heating these ternary solid mixtures, three eutectic reactions have been observed: LiPO₃+Pb(PO₃)₂→Liquid at a temperature of 793 K(1) LiPO₃+Pb₂Li(PO₃)₅→Liquid at a temperature of 843 K (2) Pb₂Li(PO₃)₅+Pb(PO₃)₂→Liquid at a temperature of 891 K (3) The metastable liquid phase appears in the system at temperature of 793 K. DTA experiments performed on the binary LiPO₃-Pb(PO₃)₂ mixtures, show a superposition of two diagrams. The first one is metastable and the second represents the stable equilibrium phase diagram. Measurements of liquid enthalpy of binary LiPO₃-Pb(PO₃)₂ system at temperature of 979.65 K were reported. The corresponding values were very small and so the binary system can be considered as athermal. Assuming an ideal behaviour, the liquidus curves in the metastable diagram were calculated and the eutectic reaction (LiPO₃-Pb(PO₃)₂→Liquid) was confirmed at 793 K. This revised version was published online in August 2006 with corrections to the Cover Date.     

TEM-characterization of rapidly solidified Nb-Al ribbons

In rapidly solidified eutectic Nb-Al alloys a change in morphology from a lamellar microstructure to a globular anomalous eutectic one has been observed. This behavior results from the decomposition of an intermediate metastable tetragonal σ*-Nb₂Al phase. By means of TEM, electron diffraction and EDXS this metastable phase was characterized and the solidification behavior via different transition steps of the metastable σ*-Nb₂Al was elucidated.     

The interaction of the theophylline metastable phase with water vapor

The conditions of hydration of the stable and metastable theophylline phases were determined. Two-phase metastable phase/monohydrate and stable phase/monohydrate equilibrium pressures were measured at 25, 30, and 35°C. The metastable phase began to react with water vapor at lower relative humidities than the stable phase. Processes that occurred with the metastable and stable theophylline phases over various water pressure ranges were considered. The metastable phase exhibited an unusual behavior at 25°C and relative humidity 47%. At constant water vapor pressure and temperature, theophylline was initially hydrated and then lost water and again became anhydrous. Two consecutive processes occurred in the system, the formation of theophylline monohydrate from the metastable phase and its decomposition to the stable phase. The ratio between the rates of these processes determined the content of the monohydrate at the given time moment.     

Solid–liquid metastable equilibria in the quaternary system (NaCl–KCl–CaCl2–H2O) at 288.15 K

The solubilities and the physicochemical properties (densities, viscosities, refractive indices, conductivities, and pH) in the liquid–solid metastable system (NaCl–KCl–CaCl₂–H₂O) at 288.15 K have been studied using the isothermal evaporation method. Based on the experimental data, the dry-salt phase diagram, water-phase diagram and the diagram of physicochemical properties vs. composition in the system were plotted. The dry-salt phase diagram of the system includes one three-salt co-saturated point, three metastable solubility isotherm curves, and three crystallization regions corresponding to sodium chloride, potassium chloride and calcium chloride hexahydrate. Neither solid solution nor double salts were found. Based on the extended Harvie–Weare (HW) model and its temperature-dependent equation, the values of the Pitzer parameters β⁽⁰⁾, β⁽¹⁾, C for NaCl, KCl and CaCl₂, the mixed ion-interaction parameters θ_Na,K, θ_Na,Ca, θ_K,Ca, Ψ_Na,K,Cl, Ψ_Na,Ca,Cl, Ψ_K,Ca,Cl, the Debye–Hückel parameter A and the standard chemical potentials of the minerals in the quaternary system at 288.15 K were obtained. In addition, the average equilibrium constants of metastable equilibrium solids at the same temperature were obtained using a method derived from the activity product constant for the metastable system. Using the standard chemical potentials of the minerals and the average equilibrium constants of solids at equilibrium, the solubility predictions for the quaternary system are presented. A comparison between the calculated and experimental results shows that the predicted solubilities obtained with the extended HW model using the average equilibrium constants agree well with experimental data.     

Metastable dissociation dynamics of molecular cluster ions

Metastable uni-cluster dissociation for several hydrogen-bonded and van der Waals cluster ions are observed via resonance-enhanced two-photon ionization reflectron time-of-flight (TOF) mass spectrometry. All of the cluster ions studied show evaporation of a single molecule from the respective parent cluster ions as dominant metastable decay processes. Furthermore, the averaged metastable evaporation rate constants (k _evap) of these cluster ions in a fixed time domain of 0.2–50 µs are obtained by analyzing the relative intensity of metastable ion peaks due to evaporation in the acceleration and the field-free drift regions of the TOF mass spectrometer. An intensity anomaly in some of the observed metastable ion peaks, indicative of magic number stability of the cluster ion, is also presented.     

Phase relations in the CaOIrO2Ir system in air

The equilibrium phase relations for the CaOIrO₂Ir system were determined in air using the quenching technique. The system contains three stable compounds 4CaO·IrO₂, 2CaO·IrO₂, and CaO·IrO₂; they dissociate to an oxide phase, Ir metal, and oxygen at 1240, 1170, and 1135°C, respectively. A metastable form of CaO·IrO₂ occurs at temperatures between 900 and 1100°C. Indexed X-ray diffraction powder patterns of all compounds are given.