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1.
A method based on Pitzer's model has been used for calculation of the solubilities of carnallite type double salts crystallizing in the systems MeX–MgX2–H2O (Me=Li, NH4, K, Rb, Cs; X=Cl, Br). The solubility of congruently soluble double salts was also determined experimentally at 25–75°C. The results from studies of the solubility diagrams of ternary carnallite type water-salt systems over a wide temperature range are summarized. It is found that the width of the crystallization region for each of the salts can be explained by the relative differences in the solubilities of the ternary solution components (MeX, MgX2·6H2O and MeX·MgX2·6H2O) and by a change of temperature, and by the effect of temperature on the solubility. A method is proposed for calculating Pitzer's ternary parameters of interionic interaction (MN and MNX) on the basis of experimental data for the solubility in water of the double salts crystallizing in the corresponding ternary water-salt systems.  相似文献   

2.
Investigation of the aqueous lithium and magnesium halide systems   总被引:1,自引:0,他引:1  
The solubilities of the system LiBr–MgBr2–H2O have been investigated at 25°C and 50°C. It is established that the system is of a simple eutonic type. Pitzer's model is used for calculating the thermodynamic functions needed for plotting the solubility isotherms of the systems LiX–MgX2–H2O (X=Cl, Br) at 25°C. According to calculations made, the Gibbs energy of formation of LiCl·MgCl2·7H2O from simple salts is rm=–2.01 kJ-mol–1, while the value fm=–2748 kJ-mol–1 corresponds to formation from the elements.  相似文献   

3.
The formation of carnallite type double salts by grinding mixtures of hydrated magnesium halide and alkali halides with the same anions was investigated by X-ray diffraction, infrared spectroscopy and thermal analysis. Carnallite (KMgCl3·6H2O), cesium-carnallite (CsMgCl3·6H2O), bromo-carnallite (KMgBr3·6H2O) and cesium-bromo-carnallite (CsMgBr3·6H2O) were formed by grinding mixtures of MgCl2·6H2O with KCl or CsCl and MgBr2·6H2O with KBr or CsBr, respectively. Hydrated solid solutions of magnesium in potassium or cesium halides were obtained from that portion of potassium and cesium halides which did not take part in the formation of the double salt.  相似文献   

4.
Solubility in the ternary systems MgBr2-NR4Br-H2O (R = Me, Et, Bu) at 25°C was determined by the isothermal saturation method. A comparative analysis of phase diagrams was fulfilled. The results obtained were interpreted in the context of competition between hydration and association processes in water-salt systems. The structure of double salts NMe4Br·MgBr2·6H2O and NEt4Br·MgBr2·8H2O was determined, and the possibility for predicting compositions of crystallizing double salts on the basis of crystallographic characteristics of ions was analyzed.  相似文献   

5.
A simple method for determination of the hydrate numbers of saturating multi-hydrate salts in developed. The method demonstrated for scandium sulfate is based upon estimation of the enthalpy of solution of the hydrates from the solubility smoothing equations. It is shown that in the Sc2(SO4)3–H2O system, contrary to common opinion, the equilibrium solid phases are: Sc2(SO4)3.6H2O at 273–295 K, Sc2(SO4)3.5H2O at 295–333 K and Sc2(SO4)3.4H2O at 333–373 K. The solubility smoothing equations for the hexa-, penta- and tetrahydrate of scandium sulfate are given.  相似文献   

6.
Isopiestic results are reported for the quaternary system H2O–NaCl–Na2SO4–MgSO4. The excess free energies for mixing the double salt Na2 Mg(SO4)2 with NaCl are fairly large and negative, as also are the free energies for mixing the three salts to form the quaternary aqueous system.  相似文献   

7.
The solubilities of the ternary systems Cu(NO3)2–Ca(NO3)2–H2O and Cu(NO3)2–Mg(NO3)2–H2O at 25°C were calculated from the solubility data for the binary systems by using the Pitzer equations. The calculated solubility isotherms were confirmed experimentally. The activity coefficients of the components, the osmotic coefficient, and the activity of water were calculated from the experimental isotherms.  相似文献   

8.
Laboratory X‐ray powder diffraction data were used to investigate the dehydration process of magnesium bromide hexahydrate in the temperature range 300 K ≤ T ≤ 420 K. By heating of the as synthesized hexahydrate (MgBr2 · 6H2O, observed in the temperature range 300 K ≤ T ≤ 349 K), three lower hydrates can be obtained in overlapped temperature regions: MgBr2 · 4H2O (332 K ≤ T ≤ 367 K), MgBr2 · 2H2O (361 K ≤ T ≤ 380 K) and MgBr2 · H2O (375 K ≤ T ≤ 390 K). Although the crystal structure of the hexahydrate was published almost eighty years ago, there are no data on the structures of the lower hydrates. The crystal structures are reported and are found to be isotypical with the structures of the respective chlorides. The structure of MgBr2 · 6H2O is characterized by discrete Mg(H2O)6 octahedra and is the only hydrate of this group that contains unbonded Br anions. MgBr2 · 4H2O is composed of discrete MgBr2(H2O)4 octahedra, and the structure was found to be disordered. The crystal structure of MgBr2 · 2H2O is formed by single chains of edge‐sharing MgBr4(H2O)2 octahedra, while in the case of MgBr2 · H2O double chains of edge‐shared MgBr5H2O are formed. By increasing the temperature, as expected, positive thermal expansion was evidenced. Thermal expansion coefficients, based on the changes of the unit cell parameters, were derived for the following hydrates: MgBr2 · 6H2O, MgBr2 · 4H2O, and MgBr2 · 2H2O.  相似文献   

9.
 The solubilities in the systems Rb2SeO4=ZnSeO4=H2O and Cs2SeO4=ZnSeO4=H2O at 25°C were studied by the method of isothermal decrease of supersaturation. Comparatively wide crystallization fields of the double salts Rb2Zn(SeO4)2ċ6H2O and Cs2Zn(SeO4)2ċ6H2O are observed in the solubility diagrams. The double salts form monoclinic crystals which are isostructural with those of the corresponding rubidium and cesium zinc sulfate hexahydrates. TG and TDA measurements indicate that the double salts lose their crystallization water in one step in the temperature intervals of 50–160°C (rubidium salt) and 70–150°C (cesium salt).  相似文献   

10.
Summary.  The solubilities in the systems Rb2SeO4=ZnSeO4=H2O and Cs2SeO4=ZnSeO4=H2O at 25°C were studied by the method of isothermal decrease of supersaturation. Comparatively wide crystallization fields of the double salts Rb2Zn(SeO4)2ċ6H2O and Cs2Zn(SeO4)2ċ6H2O are observed in the solubility diagrams. The double salts form monoclinic crystals which are isostructural with those of the corresponding rubidium and cesium zinc sulfate hexahydrates. TG and TDA measurements indicate that the double salts lose their crystallization water in one step in the temperature intervals of 50–160°C (rubidium salt) and 70–150°C (cesium salt). Received March 14, 2000. Accepted (revised) June 5, 2000  相似文献   

11.
The RbCl · MgCl2 · 6H2O? NH4Cl · MgCl2 · 6H2O? H2O and CsCl · MgCl2 · 6H2O? NH4Cl · MgCl2 · 6H2O? H2O systems have been investigated at 50°C. The formation of continuous series of mixed crystals is observed. An almost complete coincidence of the distribution coefficients values of the components between the solid and liquid phases determined experimentally and calculated theoretically using only solubility data for the two double salts has been established. The 2 RbCl · CoCl2 · 2H2O? RbCl · MgCl2 · 6H2O? H2O system has been studied at 25°C. It has been established that this system belongs to the simple eutonic type. The two double salts form no mixed crystals between each other. This fact is explained by the different character of the metal-ligand interaction of Mg2+ and Co2+ ions in aqueous halide systems.  相似文献   

12.
Reviewing the literature solubility isotherms in the ternary systems K2SO4–MSO4–H2O (M = Co, Ni, Cu, Zn) revealed a lack at ambient temperatures. The solid–liquid phase equilibria have been determined in the systems K2SO4–MSO4–H2O (M = Co, Ni, Cu) at T = 313 K. With increasing bivalent metal sulfate concentration, the solubility of potassium sulfate rises until the two-salt point is reached. Reciprocally, the solubility of the bivalent metal sulfate hydrates (CoSO4·7H2O, α-NiSO4·6H2O, CuSO4·5H2O) increases with rising potassium sulfate concentration. In all three systems the double salts of Tutton's type K2SO4·MSO4·6H2O (M = Co, Ni, Cu) are formed.  相似文献   

13.
Density functional B3LYP method with 6-31++G** basis set is applied to optimize the geometries of the luteolin, water and luteolin–(H2O)n complexes. The vibrational frequencies are also studied at the same level to analyze these complexes. We obtained four steady luteolin–H2O, nine steady luteolin–(H2O)2 and ten steady luteolin–(H2O)3, respectively. Theories of atoms in molecules (AIM) and natural bond orbital (NBO) are used to investigate the hydrogen bonds involved in all the systems. The interaction energies of all the complexes corrected by basis set superposition error, are within −13.7 to −82.5 kJ/mol. The strong hydrogen bonding mainly contribute to the interaction energies, Natural bond orbital analysis is performed to reveal the origin of the interaction. All calculations also indicate that there are strong hydrogen bonding interactions in luteolin–(H2O)n complexes. The OH stretching modes of complexes are red-shifted relative to those of the monomer.  相似文献   

14.
Crystallization of 2RbBr · MnBr2 · 2H2O, the only double salt obtained under standard conditions from saturated aqueous rubidium–manganese bromide solutions, was theoretically predicted using the hard and soft Lewis acids and bases concept and Pauling's rules. The RbBr—MnBr2—H2O system was thermodynamically simulated by the Pitzer model assuming a solubility diagram of three branches only: RbBr, 2RbBr · MnBr2 · 2H2O and MnBr2 · 4H2O. The theoretical result was experimentally proved at 25°C by the physicochemical analysis method and formation of the new double salt 2RbBr · MnBr2 · 2H2O was established. It was found to crystallize in a triclinic crystal system, space group –P1, a = 5.890(1) Å, b = 6.885(1) Å, c = 7.367(2) Å, = 66.01(1)°, = 87.78(2)°, = 84.93(2)°, V = 271.8(1) Å3, Z = 1, D x = 3.552 g-cm–3. The binary and ternary ion interaction parameters were calculated and the solubility isotherm was plotted. The standard molar Gibbs energy of the synthesis reaction, rG m o , of the double salt 2RbBr · MnBr2 · 2H2O from the corresponding simple salts RbBr and MnBr2 · 4H2O, as well as the standard molar Gibbs energy of formation, fG m o , and standard molar enthalpy of formation fH m o of the simple and double salts were calculated.  相似文献   

15.
Characteristics of the ion pairs HCOO·Na+·H2O, HCOO·K+·H2O, and also Na+·H2O and K+·H2O were calculated by the nonempirical Hartree—Fock—Roothan linear-combination-of-atomic-orbitals self-consistent-field (SCF) molecular-orbital method in a two-exponent Dunning basis using an extended set of Huzinaga—Dunning Gaussian functions. The basis was supplemented by polarization functions ofd type for the oxygen atom andp type for the H atom and also by diffusion functions ofp type for the oxygen atom. Characteristics of the ion pairs HCOO·Li+ and HCOO·Na+ were calculated taking into account the electronic correlation according to the Möller — Plesset second-order perturbation theory. Significant quantitative difference was observed in the hydration of ionogens and free cations. The stability of the ionogens HCOOMe in aqueous solutions, increasing from Li+ to Cs+, is not explained by the difference between the energies of complexation and the energies of hydration of the cations. The better solubility of the salt molecule with a cation of smaller radius is due to the higher degree of hydration of that ionogen.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 12, pp. 2700–2707, December, 1992.  相似文献   

16.
A platinum-lined, flowing autoclave facility is used to investigate the solubility/phase behavior of zinc(II) oxide in aqueous sodium phosphate solutions at temperatures between 17 and 287°C. ZnO solubilities are observed to increase continuously with temperature and phosphate concentration. At higher phosphate concentrations, a solid phase transformation to NaZnPO4 is observed. NaZnPO4 solubilities are retrograde with temperature. The measured solubility behavior is examined via a Zn(II) ion hydrolysis/complexing model and thermodynamic functions for the hydrolysis/complexing reaction equilibria are obtained from a least-squares analysis of the data. The existence of two new zinc(II) ion complexes, Zn(OH)2(HPO4)2– and Zn(OH)3(H2PO4)2–, is reported for the first time. A summary of thermochemical properties for species in the systems ZnO–H2O and ZnO–Na2O–P2O5–H2O is also provided.  相似文献   

17.
The solid—liquid equilibria of the ternary system H2O—Al(NO3)3—Mg(NO3)2 were studied at –30, –20, –10 and 0°C by using a synthetic method which allows to detemine all the characteristic points of isothermal sections. The stable solid phases which appear are respectively: ice, Al(NO3)3·9H2O, Mg(NO3)2·9H2O and Mg(NO3)2·6H2O. Neither double salts nor mixed crystals are observed in the temperature and composition field studied. Polytherm diagram layout show two invariant transformations correspond with an eutectic point and a peritectic point.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

18.
Complexation in the Co(II)–H6X–H2O, Ni(II)–H6X–H2O, and Co(II)–Ni(II)–H6X–H2O systems (H6X is nitrilotrimethylenephosphonic acid) was studied by spectrophotometry. The formation of binuclear complexonates Ni2H2X · 7H2O, Co2H2X · 5H2O, and NiCoH2X · 6H2O was demonstrated. These compounds were isolated from the solution, their composition was determined, the thermal stability was studied, and the kinetic parameters of dehydration were calculated.  相似文献   

19.
Quantum mechanical methods have been applied to thecis-ONOO-H2O,cis-ONOO-(H2O)2 andtrans- ONOO-H2O complexes. Equilibrium geometries, binding energies, net atomic charges and vibrational frequencies are presented for several different arrangements. The MØller-Plessett second-order perturbation (MP2) method predicted shorter hydrogen bonds than the SCF method, but the computed Hartree-Fock (HF) binding energies are similar to counterpoise corrected MP2 values. The geometry changes of ONOO and water after solvation are examined. The ONOO and H2O bond length changes follow typical hydrogen bond structural trends, whereas bond angles in ONOO are unaffected when the hydrogen bond is formed, similar to the conclusions from NO 2 -(H2O) n HF/6-31G studies and Monte Carlo simulations. Thecis-ONOO-(H2O) n frequencies are compared with the solution Raman spectrum and with calculations on isolated ONOO.  相似文献   

20.
The bromide minerals solubility in the mixed system (m1NaBr + m2MgBr2)(aq) have been investigated at T = 323.15 K by the physico-chemical analysis method. The equilibrium crystallization of NaBr·2H2O(cr), NaBr(cr), and MgBr2·6H2O(cr) has been established. The solubility-measurements results obtained have been combined with all other experimental equilibrium solubility data available in literature at T = (273.15 and 298.15) K to construct a chemical model that calculates (solid + liquid) equilibria in the mixed system (m1NaBr + m2MgBr2)(aq). The solubility modeling approach based on fundamental Pitzer specific interaction equations is employed. The model gives a very good agreement with bromide salts equilibrium solubility data. Temperature extrapolation of the mixed system model provides reasonable mineral solubility at high temperature (up to 100 °C). This model expands the previously published temperature variable sodium–potassium–bromide and potassium–magnesium–bromide models by evaluating sodium–magnesium mixing parameters. The resulting model for quaternary system (Na + K + Mg + Br + H2O) is validated by comparing solubility predictions with those given in literature, and not used in the parameterization process. Limitations of the mixed solution models due to data insufficiencies at high temperature are discussed.  相似文献   

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