Prediction of Electrolyte Solubilities from Minimal Thermodynamic Information

Summary.  A method is proposed that permits the proper extrapolation of thermodynamic quantities represented by the Pitzer equations from 25°C to other temperatures. The new method, which assumes temperature independent heat capacities, was tested for the NaCl*H₂O system and found very satisfactory. A new evaluation of the Na₂CO₃*H₂O system according to the CALPHAD method is presented, and solubilities for the quaternary Na₂CO₃*NaCl*NaOH*H₂O and its ternary subsystems are predicted. Limitations of (i) these predictions and of (ii) the Pitzer model regarding extrapolations to high molalities are discussed. Received April 20, 2001. Accepted May 2, 2001     

A combined method for investigating solubility and determining the composition of equilibrium solid phases saturating eutonic solutions in a NaCl-Na2SO4-Na2CO3-H2O system at 50°C

The composition of equilibrium solid phases NaCl, Na₂SO₄, Na₂CO₃ · 2Na₂SO₄ (berkeyite) and NaCl, Na₂CO₃ · H₂O, Na₂CO₃ · 2Na₂SO₄ (without preparative determination), saturating E₁ and E₂ eutonic solutions respectively, was established via nonvariant area boundary determination in a NaCl-N₂SO₄- Na₂CO₃-H₂O system at 50°C with the use of a combined method.     

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.     

Controlling Complexation Behavior of Early Lanthanides via the Subtle Interplay of their Lewis Acidity with the Chemical Stability of 5,5'-(Azobis)tetrazolide

Two novel nitrogen-rich lanthanide compounds of 5,5'-(azo bis)tetrazolide (ZT) were synthesized and structurally characterized. The dinuclear, isostructural compounds [Ce₂(ZT)₂CO₃(H₂O)₁₂] · 4 H₂O ( 1 ) and [Pr₂(ZT)₂CO₃(H₂O)₁₂] · 4H₂O ( 2 ) were synthesized via two independent routes. Compound 1 was obtained after partial Lewis acidic decomposition of ZT by Ce^IV in aqueous solution of (NH₄)₂Ce(NO₃)₆ and Na₂ZT. Compound 2 was obtained by crystallization from aqueous solutions of Pr(NO₃)₃, Na₂ZT, and Na₂CO₃. By X-ray diffraction analysis at 200 K, it was found that the trivalent lanthanide cations are bridged by a bidentate carbonato ligand and each cation is further coordinated by six H₂O ligands and one ZT ligand thus being ninefold coordinated.     

High-temperature equilibria and critical phenomena in the Na2CO3-NaCl-H2O and Na2CO3-Na2WO4-H2O systems

Phase equilibria in the Na₂CO₃-NaCl-H₂O and Na₂CO₃-Na₂WO₄-H₂O ternary systems formed by type 1 salts (NaCl, Na₂WO₄) and a type 2 salt (Na₂CO₃) were experimentally studied at temperatures from 425 to 500°C and pressures from 30 to 160 MPa with the contents of type 1 salts from 10 to 30 wt %. Transition from supercritical homogeneous fluid equilibria of the Na₂CO₃-H₂O system to heterogeneous equilibria of the title ternary systems was studied in the presence or absence of liquid phase immiscibility in the type 1 subsystems.     

298.16 K Na＋, K＋, Mg2＋//Cl－, NO3－-H2O五元体系的相平衡研究

采用等温溶解平衡法研究了五元体系Na^＋, K^＋, Mg^2＋//Cl^－, NO₃^－-H₂O在298.16 K、氯化钠饱和时各盐的溶解度和饱和溶液的物化性质(密度, 电导率)以及四元体系Na^＋, Mg^2＋//Cl^－, NO₃^－-H₂O的相平衡关系. 研究表明: 在298.16 K, 氯化钠饱和时该五元体系溶解度相图由六个结晶区、九条单变量溶解度曲线和四个零变量点构成, 六个结晶区分别对应于NaNO₃＋NaCl, KNO₃＋NaCl, KCl＋NaCl, Mg(NO₃)₂•6H₂O＋NaCl, MgCl₂•6H₂O＋NaCl和复盐KCl•MgCl₂•6H₂O＋NaCl; 在298.16 K时, 该四元体系的相图由四个结晶区、五条单变量溶解度曲线和二个零变量点构成, 四个结晶区分别对应于NaNO₃, NaCl, Mg(NO₃)₂•6H₂O, MgCl₂•6H₂O.     

Thermodynamic Properties of Quaternary Aqueous Solutions of Chlorides Charge-type 1-1*1-1*2-1: NH4Cl + NaCl + YCl2 + H2O with Y ≡ Mg2+, Ca2+, and Ba2+

Thermodynamic properties of quaternary aqueous solutions of mixed chlorides of 1-1*1-1*2-1 charge type with the cations (Na⁺, NH₄ ⁺; Mg²⁺, Ca²⁺, Ba²⁺) were determined using the hygrometric method. The quaternary systems NH₄Cl + NaCl + MgCl₂ + H₂O, NH₄Cl + NaCl + CaCl₂+ H₂O, and NH₄Cl + NaCl + BaCl₂ + H₂O have been studied at 25 °C. The water activities were measured at total molalities from 0.44 mol⋅kg⁻¹ to saturation for different ionic-strength fractions y of NH₄Cl, y=(0.20,0.50,0.80), and different ionic strength ratios z for other solutes, z=(0.20,0.50 and 0.80) for each value of y. The obtained data allows the calculation of osmotic coefficients.     

Entwässerung von Kristallhydraten als Verfahren zur Reinigung von Salzen, 5. Mitt.

Zusammenfassung Es wurde die quantitative Änderung der nicht-isomorphen Verunreinigung der Kristallmasse mit NaCl bei der Entwässerung des Na₂CO₃ · 10 H₂O untersucht — sowohl in seiner gesättigten Lösung bei der Übergangstemperatur als auch unter der Einwirkung einiger organischer Lösungsmittel auf das Kristallhydrat, einschließlich dem eigentlichen Entwässerungsprozeß bei 22±0,5 °C. Es wurde festgestellt, daß der von struktureller Änderung begleitete Entwässerungsprozeß eine wesentliche Verminderung der Verunreinigung im entwässerten Produkt in beiden Fällen hervorruft. Bei der Temperatur, bei welcher Na₂CO₃ · 7 H₂O in seiner gesätt. Lösung ohne strukturelle Änderung in Na₂CO₃ · H₂O übergeht, bleibt die Menge der Verunreinigung praktisch unverändert.

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Dehydration of crystal hydrates as a method of purifying salts, V: Dehydration ofNa ₂Co₃ · 10 H₂O with organic solvents, also at the temperature of its transformation to a saturated solution

The quantitative alteration of non-isomorphous contamination of the crystalline mass with NaCl during the dehydration of Na₂CO₃ · 10 H₂O has been investigated, both in its saturated solution at the transition temperature and in the direct treatment of the crystallohydrate with a number of organic solvents, including the dehydration process itsself at 22±0.5 °C. It was established that the dehydration process, accompanied with a structural alteration, provokes in both cases a substantial decrease of the admixture in the dehydrate product. At the temperature, at which Na₂CO₃ · 7 H₂O in its saturated solution is transformed into Na₂CO₃ · H₂O without structural changes, the amount of admixture remains practically the same.

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Rate Determination of the CO2* Chemiluminescence Reaction CO + O + M CO2* + M

Electronically excited carbon dioxide (CO₂*) is known for its broadband emission, and its detection can lead to valuable information; however, owing to its broadband characteristics, CO₂* is difficult to isolate experimentally, and its chemical kinetics are not well known. Although numerous works have monitored CO₂* chemiluminescence, a full kinetic scheme for the excited species has yet to be developed. To this end, a series of shock‐tube experiments was performed in H₂‐N₂O‐CO mixtures highly diluted in argon at conditions where emission from CO₂* could be isolated and monitored. These results were used to evaluate the kinetics of CO₂*, in particular the main CO₂* formation reaction CO + O + M CO₂* + M (R1). Based on collision theory, the quenching chemistry of CO₂* was estimated for 11 collision partners. The final mechanism developed for CO₂* consists of 14 reactions and 13 species. The rate for (R1) was determined to within about ±60% using low‐pressure experiments performed in five different (H₂‐)N₂O‐CO‐Ar mixtures, as follows: where R is the universal gas constant in cal/mol‐K and T is the temperature in K. Final mechanism predictions were compared with experiments at low and high pressures, with good agreement at both conditions for the temperature dependence of the peak CO₂* and the CO₂* species time histories. Comparisons were also made with previous experiments in methane–oxygen mixtures, where there was slight overprediction of CO₂* experimental trends, but with the results otherwise showing a dramatic improvement over an earlier mechanism. Experimental results and model predictions were also compared with past literature rates for CO₂*, with good agreement for peak CO₂* trends and slight discrepancies in CO₂* species time histories. Overall, the ability of the CO₂* mechanism developed in this work to reproduce a range of experimental trends represents an important improvement over the existing knowledge base on chemiluminescence chemistry.     

Testing the retardancy effect of various inorganic chemicals on smoldering combustion of Pinus halepensis needles

The fire retarding performance of 28 different inorganic chemical substances was tested by measuring the relative particle fire hazard properties of Pinus halepensis needles treated with these chemicals. The tests were performed using a new method, based on a specifically designed apparatus for monitoring the forest species temperature, under precisely controlled temperature and static air atmosphere conditions. The relative ignition and smoldering combustion properties determined were: the ignition delay time, the combustion rate, the heat content and the mass residue of forest samples. The key elements for the effectiveness of fire retardants were the delay of ignition and the reduction of heat and combustion rate. The chemicals examined were: Cu, Fe, Al₂O₃, Fe₂O₃, SiO₂·H₂O, NaHCO₃, KI, KBr, KCl, NaCl, CaCO₃, MnSO₄·5H₂O, CuSO₄·5H₂O, MgCl₂·6H₂O, Na₂B₄O₇·10H₂O, Na₂HPO₄, Na₂CO₃, Na₂SiO₃, ZnSO₄·7H₂O, Zn₃(PO₄)₂·2H₂O, NH₄Br, NH₄Cl, NH₄HCO₃, (NH₄)₂CO₃, NH₄H₂PO₄ (MAP), (NH₄)₂SO₄ (AS), (NH₄)₂HPO₄ (DAP) and a commercial retardant containing both DAP and AS. Among them the best performance was exhibited by ammoniac phosphates, followed by ammoniac sulfates and silica.     

Fundamentals in CO_2 capture of Na_2CO_3 under a moist condition

Capacity and kinetics of CO_2 capture of Na_2CO_3 were studied to determine the mechanism for CO_2 sequestration under ambient conditions. Bicarbonate formation of Na_2CO_3 was examined by a thermogravimetric analysis(TGA) under various CO_2 and water vapor concentrations and the accompanying structural changes of Na_2CO_3 were demonstrated by X-ray diffraction(XRD). Morphological variations were observed during the reaction of CO_2 capture through scanning electron microscope(SEM). Structural changes and morphological variations, which occurred during the course of the reaction, were then connected to the kinetic and exothermic properties of the CO_2 capture process from the XRD and SEM measurements. The results showed that the bicarbonate formation of Na_2CO_3 has two different pathways.For higher CO_2 and H_2O concentrations, the bicarbonate formation proceeded effectively. However, for lower CO_2 and H_2O concentrations, the reactions were more complicated. The formation of Na_2CO_3·H_2O from Na_2CO_3 as the first step, followed by the subsequent formation of Na_5H_3(CO_3)_4, and then the bicarbonate formation proceeds. To understand such fundamental properties in CO_2 capture of Na_2CO_3 is very important for utilization of Na_2CO_3 as a sorbent for CO_2 capture.     

Chemie der Seltenerdmetalle, 8. Mitt.: Tartratkomplexe des Lanthans

Zusammenfassung Es wurde die systematische Untersuchung des Systems im sauren Bereich durchgeführt und die Stoffe der Zusammensetzung^* La₂(H₂ T)₃·9 H₂O und H[La(H₂ T)₂]·3 H₂O isoliert. Diese wurden röntgenographisch untersucht und ihre thermische Analyse durchgeführt. Die IR-Absorptionsbanden werden zugeordnet. Auf Grund von pH-Messungen wurden die Dissoziationskonstanten bestimmt.

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A systematic investigation of the system in the acidic range was performed, and the compounds^* La₂(H₂ T)₃·9 H₂O and H[La(H₂ T)₂]·3 H₂O were isolated. X-ray powder diagrams were taken, and their thermal analysis carried out. The IR-absorption bands were assigned, and the dissociation constants, based on pH-measurements determined.

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Analyse physico-chimique du système quaternaire Na+,Mn2+/Cl–,(H2PO2)–//H2O

To elaborate a new method of synthesis of manganese hypophosphite based on an exchange reaction, the solubility in the Na⁺,Mn²⁺/Cl^–,(H₂PO₂)^–//H₂O system has been investigated by the isothermal method at 25 °C. For the system in question, an invariant quartet point has been determined. Its composition has been determined as following: NaCl 4.12, MnCl₂ 41.50, Mn(H₂PO₂)₂ 2.06 and H₂O 52.32 (wt.%). The crystallisation field of Mn(H₂PO₂)₂·H₂O occupies 82.9% of the total.     

Conversion of yttrium-aluminum garnet to soluble forms as a result of mechanochemical treatment

Summary The changes in the solubility and in the phase composition of yttrium-aluminum garnet (YAG) as a result of its mechanochemical treatment for 2 h in a planetary ball mill together with H₃BO₃ and Na₂CO₃ (mole ratio H₂BO₃/Na₂CO₃=4) in ratios (H₃BO₃+Na₂CO₃)/YAG=2,4, and 9 are studied. At a ratio of 9, the yield of yttrium in the water solution obtained upon treatment of the activated mixture at 90 °C (50 cm³ water/g sample) reaches 85%. Its content in the same solution is above 93% relatively to the sum Y+Al.

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Umwandlung von Yttrium-Aluminium-Granat in lösliche Formen durch mechanochemische Behandlung

Zusammenfassung Die Änderungen bezüglich Löslichkeit und Phasenzusammensetzung von Yttrium-Aluminium-Granat (YAG) als Ergebnis einer zweistündigen mechanochemischen Behandlung in einer Kugelmühle zusammen mit H₃BO₃ und Na₂CO₃ (Molverhältnis H₃BO₃/Na₂CO₃=4) bei (H₃BO₃+Na₂CO₃)/YAG-Verhältnissen von 2, 4 und 9 wurden untersucht. Bei einem Verhältnis von 9 erreicht die Ausbeute an Yttrium in der wäßrigen Lösung nach Behandlung der aktivierten Mischung bei 90 °C (50 cm³ H₂O pro Gramm) 85%. Relativ zur Summe Y+Al beträgt der Yttriumgehalt 93%.

     

A study of the thermodynamic properties and dehydration reaction kinetics of some salt-hydrates

Correlations were determined between heat capacity and temperature and phase change enthalpy of Ba(OH)₂·8H₂O. The phase diagram and DSC curve of the binary system Na₂CO₃·10H₂O?Na₂HPO₄·12H₂O were determined The kinetics of the dehydrating reaction of Ba(OH)₂·8H₂O, Na₂CO₃·10H₂O and Na₂HPO₄·12H₂O were measured and theoretically analyzed by TG.     

Synthesis and physicochemical characterization of nanocrystalline chitosan-containing calcium carbonate apatites

The CaCl₂-(NH₄)₂HPO₄-NH₄HCO₃-(C₆H₁₁NO₄) _n -H₂O system at 25°C has been investigated by the solubility (Tananaev’s residual concentration) method and pH measurements. Coprecipitation conditions have been determined for nanocrystalline type A and B calcium carbonate apatites. Type A: Ca₁₀(PO₄)₆(CO₃) _x (OH)_{2 − 2x} · yC₆H₁₁NO₄ · zH₂O (x = 0.2, 0.5, 1.0; y = 0.1, 0.3, 0.5; z = 5.3−6.7); type B: Ca₁₀[(PO₄)_5.7(CO₃)_0.45]CO₃ · 0.3C₆H₁₁NO₄ · 9H₂O, and Ca₁₀[(PO₄)_5.55(CO₃)_0.675]CO₃ · 0.3C₆H₁₁NO₄ · 9.2H₂O. The solid phases have been characterized by chemical analysis, X-ray diffraction, thermogravimetric analysis, and IR spectroscopy.     

Darstellung und Struktur der ersten gemischten Alkalimetallhydrogencarbonate NaA2[H(CO3)2] · 2H2O mit A = K,Rb

Preparation and Crystal Structure of the First Mixed Alkalimetal Hydrogencarbonates NaA₂[H(CO₃)₂] · 2H₂O with A = K, Rb The new hydrogencarbonates NaK₂[H(CO₃)₂] · 2H₂O (Pnma, a = 934.07(13) pm, b = 789.31(10) pm, c = 1142.1(5) pm, V_EZ = 842.0(4) · 10⁶ pm³, Z = 4, R1 (I ? 2σ(I)) = 0.023, wR2 = 0.066 for 989 reflections) and NaRb₂[H(CO₃)₂] · 2H₂O (Pnma, a = 948.24(11) pm, b = 811.37(9) pm, c = 1189.0(2) pm, V_EZ = 914.8(2) · 10⁶ pm³, Z = 4, R1 (I ≤ 2σ(I)) = 0.031, wR2 = 0.077 for 1063 reflections) were prepared from aqueous solutions. The crystal structures were determined. The isostructural compounds contain dimeric, non centrosymmetric [H(CO₃)₂]^3? anions. In NaK₂[H(CO₃)₂] · 2H₂O a short hydrogen bond (d(O … O) = 246.1(2) pm) with an asymmetric potential was detected. In NaRb₂[H(CO₃)₂] · 2H₂O a hydrogen bond with symmetric potential (d(O … O) = 247.8(5) pm) can be assumed. The IR-spectra of NaK₂[H(CO₃)₂] · 2H₂O and Na₃[H(CO₃)₂] · 2H₂O are compared.     

H2-induced CO adsorption and dissociation over Co/Al2O3 catalyst

The activation of adsorbed CO is an important step in CO hydrogenation. The results from TPSR of pre-adsorbed CO with H2 and syngas suggested that the presence of H2 increased the amount of CO adsorption and accelerated CO dissociation. The H2 was adsorbed first, and activated to form H＊ over metal sites, then reacted with carbonaceous species. The oxygen species for CO2 formation in the presence of hydrogen was mostly OH^＊, which reacted with adsorbed CO subsequently via CO^＊＋OH^＊ → CO2^＊＋H^＊; however, the direct CO dissociation was not excluded in CO hydrogenation. The dissociation of C-O bond in the presence of H2 proceeded by a concerted mechanism, which assisted the Boudourd reaction of adsorbed CO on the surface via CO^＊＋2H^＊ → CH^＊＋OH^＊. The formation of the surface species （CH） from adsorbed CO proceeded as indicated with the participation of surface hydrogen, was favored in the initial step of the Fischer-Tropsch synthesis.     

The Rb analogue of grimselite,Rb6Na2[(UO2)(CO3)3]2(H2O)

The crystal structure of the Rb analogue of grimselite, rubidium sodium uranyl tricarbonate hydrate, Rb₆Na₂[(UO₂)(CO₃)₃]₂(H₂O), consists of a uranyl hexagonal bipyramid that shares three non‐adjacent equatorial edges with carbonate triangles, resulting in a uranyl tricarbonate cluster of composition [(UO₂)(CO₃)₃)]. These uranyl tricarbonate clusters form layers perpendicular to [001] and are interconnected by NaO₈ polyhedra. The title compound is isostructural with grimselite, with a reduced occupancy of the H₂O site (25% versus 50% in grimselite).     

KINETICS AND MECHANISTIC ASPECTS OF THE HYDROLYSIS REACTION OF CYCLIC PHOSPHONODITHOITES

Abstract

The hydrolysis of the cyclic phosphonodithioite C₆H₅ P(SCH(CO₂CH₂CH₃CH(CO₂CH₂CH₃)S) in aqueous acetonitrile follows a rate law that is first order in the concentration of C₆H₅ P(SCH(CO₂CH₂CH₃)CH(CO₂CH₂CH₃)S), and independent of the water concentration. The values of E_a , ΔH* and ΔS* are 10.4 k cal mol^?1, 9.6 k cal mol^?1 and -45 cal mol^?1 respectively. The isotope effect for D₂O as compared to H₂O is 2.5. A mechanism is proposed whereby a pre-equilibrium is established between the phosphonodithioite and water, with a subsequent proton transfer from water to the tricoordinate phosphorus occurring in a subsequent step. The slow step involves hydrolytic cleavage of the first phosphorus-sulfur bond. The compound 2-nitro-5-thiocyanatobenzoic acid is used to provide supporting evidence for the formation of an intermediate thiol.