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1.
Thermodynamics of formation of carnallite type double salts 总被引:1,自引:0,他引:1
Chr Balarew Chr Christov Vl. Valyashko S. Petrenko 《Journal of solution chemistry》1993,22(2):173-181
The solubility of the systems RbCl–MgCl2–H2O, RbBr–MgBr2–H2O and CsBr–MgBr2–H2O have been investigated by the physicochemical analysis method at 25°C and formation of carnallite type double salts was established. The Pitzer model is used to calculate the thermodynamic functions needed to plot the solubility isotherms of the systems. The results obtained are in good agreement with the experimental data. The free energies of formation of carnallite and bromcarnallite type double salts from simple salts and the standard molar energies of formation are estimated. 相似文献
2.
Chr Christov Chr Balarew S. Petrenko Vl. Valyashko 《Journal of solution chemistry》1994,23(5):595-604
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 rG°m=–2.01 kJ-mol–1, while the value fG°m=–2748 kJ-mol–1 corresponds to formation from the elements. 相似文献
3.
C. Christov S. Petrenko C. Balarew V. Valyashko 《Monatshefte für Chemie / Chemical Monthly》1994,125(12):1371-1382
Summary The standard method ofPitzer for predicting the solubility isotherms of systems in which solid phases with a constant composition crystallize is applied to cases when mixed crystals are formed. The four-component carnallite type systems RbCl-CsCl-MgCl2-H2O, RbCl-KCl-MgCl2-H2O, and RbCl-RbBr-MgCl2-MgBr2-H2O and the corresponding subsystems are thermodynamically simulated at 25°C. It is established that the solubility diagrams consist of crystallization regions of the simple saltsMX,MX, MgX
2·6H2O, and MgX2·6H2O and of the corresponding carnallite type double salts with the composition 1:1:6. A method of calculation of the integralGibbs energy of mixingG
mix(s) of crystals formed in water-salt systems has been proposed. The results on the systems RbCl-KCl-H2O, RbCl-RbBr-H2O, and MgCl2-MgBr2-H2O are compared with experimental data from the literature and with values calculated using various models.
Thermodynamische Simulation von Vierkomponentensystemen des Carnallit-Types
Zusammenfassung DiePitzer-Methode zur Voraussage der Löslichkeitsisothermen in Mehrstoffsystemen, in welchen feste Phasen mit konstanter Zusammensetzung auskristallisieren, wurde auch für Fälle angewendet, bei denen sich Mischkristalle bilden. Die Vierstoffsysteme RbCl-CsCl-MgCl2-H2O, RbCl-KCl-MgCl2-H2O und RbCl-RbBr-MgCl2-MgBr2-H2O, aus welchen Carnallit-Typ-Mischkristalle auskristallisieren, und die dazugehörigen Dreistoff-Randsysteme wurden bei 25°C simuliert. Man stellt fest, daß die Löslichkeitsdiagramme sowohl Kristallisationsbereiche der einfachen SalzeMX,M'X, MgX 2·6H2O und MgX 2·6H2O als auch der entsprechenden carnallitartigen Doppelsalze mit der Zuzammensetzung 1:1:6 umfassen. Eine Methode zur Berechnung derGibbs-EnergieG mix(s) für die in Wasser-Salz-Systemen gebildeten Mischkristalle wird vorgeschlagen. Die für die Systeme RbCl-KCl-H2O, RbCl-RbBr-H2O und MgCl2-MgBr2-H2O erhaltenen Ergebnisse werden mit experimentellen Literaturdaten und Resultaten von Berechnungen aufgrund verschiedener Modelle verglichen.相似文献
4.
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
5.
Double Salts Formation in the Systems MX–MeX 2–H2O (M=K,NH4, Rb,Cs; Me=Mg,Mn, Fe,Co, Ni,Cu; X=Cl,Br)
Balarew Christo Tepavitcharova Stefka 《Monatshefte für Chemie / Chemical Monthly》2003,134(5):721-734
Monatshefte für Chemie - Chemical Monthly - ?The data available on the solubility phase diagrams and on the crystallization of chloride and bromide double salts in the systems... 相似文献
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1,4-Phenylenebis(methylene) sulfonium salts were polymerized under different conditions to yield p-xylylene sulfonium salt polyelectrolytes in a broad range of molecular weights. The aqueous reaction mixture formed a reversible gel at initial monomer concentrations higher than 1.0M, but at lower concentrations it remained as an emulsion until reaction completion. The effect of reaction time on intrinsic viscosities and polymer yields for both the emulsion and the gel state is discussed. The higher yields obtained when the reaction was carried out in the presence of a water-immiscible organic solvent were apparently due to the effect of this solvent on increasing the concentration of the reactive intermediate that led to the polyelectrolyte. Both the addition of an organic solvent and the variation of the initial monomer concentrations allowed some control over the molecular weight of the polyelectrolyte formed. 相似文献
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HAI QING LIU LI NA ZHANG AKIRA TAKARAGI TAKEAKI MIYAMOTO 《Cellulose (London, England)》1997,4(4):321-327
The effect of substituent distribution on the water solubility of O-methylcellulose (MC) was re-examined to elucidate the
lower limit of the degree of substitution (DS) in water-soluble MC. To this end, a series of 2,3-MCs which are regioselectively
substituted at the C-2 and C-3 hydroxyl groups were prepared by homogeneous methylation. It was found that the lower limit
for the DS value of water-soluble 2,3-MC was almost the same as that for MCs having even distributions of substituents along
the cellulose chain as well as in the anhydroglucose units.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Sean Christie Raymond H. Dubois Robin D. Rogers Peter S. White Michael J. Zaworotko 《Journal of inclusion phenomena and macrocyclic chemistry》1991,11(2):103-114
A series of air and water stable organic cation triiodide salts have been prepared and characterized. Almost all of the salts isolated sustain liquid clathrate phases in the presence of benzene or toluene, the compositions of which were determined via1H NMR spectroscopy. Two of the salts were also characterized via X-ray crystallography in order to determine the nature of any solid state interionic interactions (1-ethylpyridinium triiodide, monoclinic,P21/c,a = 9.6031(7),b = 15.129(3),c = 8.8160(16) Å, = 104.192(11)°,Z = 4,R = 0.041 for 2463 independent observed reflections; 1,2,4-trimethylpyridinium triiodide, orthorhombic,Pbcm,a = 9.434(4), 20.176(4), 7.411(4) Å,Z = 4,R = 0.045 for 966 observed reflections). 相似文献
14.
Jos A. Fernandes 《Acta Crystallographica. Section C, Structural Chemistry》2020,76(2):117-117
A possible solution for improving the water solubility of berberine by the formation of multicomponent pharmaceutical salts provides the background for this commentary. 相似文献
15.
The effect of polymer microstructure on the solubility characteristics and propensity for interactions of polybutadiene (PBD) has been studied by means of the general solvation equation using data reported by Alessi et al. An increase in the vinyl content from 8% to 69% did not affect the propensity of PBD to interact with and n electron pairs and with dipolar — polarisable probes. In contrast, the hydrogen-bond basicity decreased due to steric hindrance from the alkene side group. 相似文献
16.
The effect of bromide salts, MBr [M=Na, (CH3)4N, (C2H5)4N, (C4H9)4N, C8H17N(CH3)3], on the first-order rate constant, k
1, of basic hydrolysis of 2,4-dinitrochlorobenzene in micelle solutions of cetyltrimethylammonium bromide has been studied.
The main results are as follows. The molar ratio concentrations of OH−, m
S
OH, on the micelle surface in the presence of different concentrations of Br− ions, were calculated on the basis of the pseudophase ion-exchange model, and there is a linear relation between k
1 and m
S
OH. The relation between k
1 and the concentrations of various bromides could be presented with a single curve, and the cations of the bromides have little
effect on k
1. Under the experimental conditions, there is a linear relation between 1/k
1 and the concentrations of Br−; thereby a new method calculating the competition binding constant between OH− and Br− from dynamic data is proposed. The hydrodynamic radii of the micelles increase with the addition of bromide salts.
Received: 1 August 2000 Accepted: 31 January 2001 相似文献
17.
We report a rheological study on the effect of adding organic salts [sodium tosylate (NaTos) and benzoic acid potassium salt
(BaPs)] on the micellar growth and structure of aqueous solutions of cethyltrimethylammonium chloride (CTAC) at a constant
molar concentration ratio [salt]/[CTAC]. The rheological data show two well-defined domains of growth characterized by scaling
laws for the surfactant concentration. The addition of NaTos leads to an unusual maximum in the viscosity-surfactant concentration
curve. Before the maximum (domain 1), the analysis of the data (η0, τR and G
0) suggests the presence of branched micelles (connections). After the maximum (domain 2), however, the exponents of the scaling
laws do not reflect either the relaxation of this branched structure or that of an entangled transient network structure.
A faster mechanism of relaxation, not yet elucidated governs their dynamics. The exponents of the power laws in the presence
of the BaPs are found, however, to be in accordance with the theory of equilibrium polymers.
Received: 15 April 1998 Accepted in revised form: 20 October 1998 相似文献
18.
T. C. Uzomah 《Journal of polymer science. Part A, Polymer chemistry》2000,38(1):43-50
The solubility equation derived from the thermodynamics of mobile order theory was used (1) to predict the solubility of three solid n‐alkanes—octadecane, dotriacontane, and hexatriacontane—in nonassociated and self‐associated liquids at 25 °C and (2) to predict the increased solubility in particular solvents with increasing temperatures. The evolution of the predicted solubility rested on the relative importance of the different terms contributing to the solubility. Generally, the fluidization of the solute presented a reluctance to the solubility. In nonassociated liquids, the balance of placing the entropy correction and the change in the nonspecific cohesion forces played up, whereas in the hydrogen‐bonded liquids, the solubility was determined by the hydrophobic effect. The effect of increasing the temperature of the dissolution of the solute was a reduction in the negative fluidization and nonspecific cohesion forces, which resulted in increased solubility. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 43–50, 2000 相似文献
19.
DTA and TG studies in air were carried out for hydrothermally prepared rhombohedral double carbonates of dolomite type, CaMg(CO3)2, CaMn(CO3)2, CdMg(CO3)2, CdMn(CO3)2 and CdZn(CO3)2. The solid decomposition products in air have been compared to those obtained under hydrothermal conditions with CO2 pressure. The dolomite [CaMg(CO3)2] decomposes in two stages both in air as well as under high CO2 pressure. The other carbonates studied, follow a single stage decomposition in air and a two stage decomposition under hydrothermal condition. In air, the manganese containing carbonates CaMn(CO3)2 and CdMn(CO3)2, decompose to form mixed oxides of CaMnO3 and CdMnO3 respectively, while CdMg(CO3)2 and CdZn(CO3)2 decompose to their respective two mono oxides.
Zusammenfassung Mittels DTA und TG in Luft werden die hydrothermisch hergestellten rhomboedrischen Doppelkarbonate (Dolomittyp) CaMg(CO3)2, CaMn(CO3)2, CdMg(CO3)2, CdMn(CO3)2 und CdZn(CO3)2 untersucht. Die in Luft erhaltenen festen Zersetzungsprodukte wurden mit denen verglichen, die unter hydrothermischen Bedingungen mit CO2-Druck entstehen. Dolomit zersetzt sich sowohl in Luft als auch unter hohem CO2-Druck in zwei Schritten. Die übrigen untersuchten Karbonate zersetzen sich in Luft in einem, unter hydrothermischen Bedingungen in zwei Schritten. In Luft zersetzen sich die magnesiumhaltigen Karbonate CaMn(CO3)2 und CdMn(CO3)2 unter Bildung der Mischoxide CaMnO3 und CdMnO3, während aus CdMg(CO3)2 und CdZn(CO3)2 jeweils die entsprechenden beiden Monoxide entstehen.相似文献
20.
Pinal R 《Organic & biomolecular chemistry》2004,2(18):2692-2699
Molecular symmetry has a pronounced effect on the melting properties and solubility of organic compounds. As a general rule, symmetrical molecules in crystalline form have higher melting temperatures and exhibit lower solubilities compared with molecules of similar structure but with lower symmetry. Symmetry in a molecule imparts a positive amount of residual entropy in the solid phase (i.e., more possible arrangements leading to the same structure). This means that the entropy of a crystal of symmetric molecules is greater than the entropy of crystal of a similar, but non-symmetric molecule. An analysis is presented relating the enthalpy, entropy and temperature of melting for an idealised system of structural isomers of different molecular symmetries. The analysis presented helps explain why often, yet not always, the crystal of a more symmetric molecule, which has greater entropy to start (closer to that of the liquid), also exhibits a greater gain in entropy upon melting, compared with the crystal of a less symmetrical molecule. The residual entropy due to molecular symmetry has the direct effect of reducing the entropy gain upon melting (a negative effect). However, molecular symmetry also exerts indirect effects on both the entropy and enthalpy of melting. These indirect effects, imposed by the condition of equilibrium melting, are positive, such that it is the balance between the direct and indirect effects what determines the value observed for the entropy of melting of the symmetric molecules. When the indirect effect of molecular symmetry is greater than its direct effect, the observed entropy gain upon melting of the more symmetrical molecule is greater than that of a less symmetrical one. 相似文献