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1.
Sodium and potassium thiocyanate complex compounds of formulae [Na(hmta)(H2O)4]22+·2SCN− (1) and [K2(hmta)(SCN)2]
n
(2) have been synthesized and characterised by IR spectroscopy, thermogravimetry coupled with differential thermal analysis,
elemental analysis and X-ray crystallography. Each sodium and potassium cation is six co-ordinated, the sodium by one monofunctional
hmta molecule, three terminal water molecules and two bridging water molecules, and the potassium by two bridging tetrafunctional
hmta molecules and four bridging tetrafunctional thiocyanate ions. The coordination polyhedra of the central atoms can be
described as distorted tetragonal bipyramids. The complex cations and anions of (1) are interconnected by multiple intramolecular
O(water)—H···N(hmta/NCS) and O(water)—H···S hydrogen bonds to the three dimensional net. In each complex cation the intramolecular
O–H···O hydrogen bonds link two terminal water molecules bonded to two metal cations. The compound (2) forms the three dimensional
hybrid network in which the classical two-dimensional coordination polymers are linked by inorganic SCN− spacers to the third-dimension. Thermal analyses show that the compounds decompose gradually in three (for 1) and two (for
2) steps with formation of Na2SO4 and K2S as the final products, respectively, for 1 and 2. 相似文献
2.
Abrosimov V. K. Ivanov E. V. Efremova L. S. Pankratov Yu. P. 《Russian Journal of General Chemistry》2002,72(5):667-674
The thermodynamic characteristics of hydration of Ar and Kr were calculated from experimental data on the solubility of Ar and Kr in solutions of urea in H2O and of deuterourea in D2O at 101325 Pa and 278.15-318.15 K. Solutions of Ar and Kr significantly differ in the value of thermodynamic effects accompanying dissolution. 相似文献
3.
The thermal decomposition process of mixtures of CoC2O4⋅2H2O (COD) or Co(HCOO)2⋅2H2O (CFD) or [Co(NH3)6]2(C2O4)3⋅4H2O (HACOT) with activated carbon was studied with simultaneous TG–DTG–DTA measurements under non-isothermal conditions in argon
and argon/oxygen admixtures. The results show that the thermal decomposition of the studied mixtures in Ar proceeds in the
same manner. It begins with the salt decomposition to Comet+CoO mixture followed by (T>680 K) the simultaneous reduction of CoO to Cometand carbon degasification. The final product of the thermal decomposition of COD-C and CFD-C mixtures, identified by XRD,
is β-Co. Cobalt contents determined in the final products fall in the range 71–78 mass%. The rest is amorphous residual carbon.
In Ar/O2 admixtures the end product is Co3O4 with ash admixture.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
Mariano Velázquez-Rivera Donald A. Palmer Richard M. Kettler 《Journal of solution chemistry》2006,35(12):1699-1730
This study measures the osmotic coefficients of {xH2SO4 + (1−x)Fe2(SO4)3}(aq) solutions at 298.15 and 323.15 K that have ionic strengths as great as 19.3 mol,kg−1, using the isopiestic method. Experiments utilized both aqueous NaCl and H2SO4 as reference solutions. Equilibrium values of the osmotic coefficient obtained using the two different reference solutions
were in satisfactory internal agreement. The solutions follow generally the Zdanovskii empirical linear relationship and yield
values of a
w for the Fe2(SO4)3–H2O binary system at 298.15 K that are in good agreement with recent work and are consistent with other M2(SO4)3–H2O binary systems. 相似文献
5.
Distributions of argon clusters (Ar
n
+
wheren=1–27) obtained in a molecular beam/time-of-flight system were analyzed in order to assess the influence of fragmentation.
The results from rudimentary pseudopotential molecular calculations were calculated to predict the most stable structures
and stabilities for the smaller argon ion sized clusters (Ar
n
+
wheren=3−9). 相似文献
6.
J. Monaselidze Maya Kiladze D. Tananashvili Shota Barbakadze A. Naskidashvili Anna Khizanishvili R. Kvavadze G. Majagaladze 《Journal of Thermal Analysis and Calorimetry》2006,84(3):613-618
The heat
effects arising at heating of Spirulina platensis
cell culture containing different quantity of water (from 98.2 to 10.5 mass%
H2O) have been studied. The hydration of Sp. pl. cells determined by the method of microcalorimetry
at 25°C (Δn) was equal to 0.32±0.02
g H2O/g of dry biomass. The heat (–Q) evolved by cells in the temperature range 5–52°C
decreased exponentially at decrease of mass% H2O and
reached zero value at 30.5±3.0 mass% H2O. The
total heat of cell denaturation did not change in the range 98.2–40.5
mass% H2O and it sharply dropped at lower values of
water. 相似文献
7.
Kazuyuki Nakai Joji Sonoda Masayuki Yoshida Masako Hakuman Hiromitsu Naono 《Adsorption》2007,13(3-4):351-356
The high resolution adsorption isotherms of N2 (77.4 K) and Ar (87.3 K) have been measured for two nonporous silicas with different silanol contents (3.3 and 0.35 OH/nm2) and for two MFI zeolite with different Al contents (Si/Al=12.5 and 500). Silanol groups and Al sites (acid sites) gives
the significant effect on the N2 isotherms at submonolayer, but the Ar isotherms are independent of silanols and Al sites. The Ar isotherms, therefore, are
preferable in calculation of microporosity of zeolites. The N2 and Ar isotherms for MFI zeolite (Si/Al=500) have been measured at temperatures of 77–94 K, from which the differential adsorption
energies of N2 and Ar are calculated. The interaction of N2 with channel surface of MFI zeolite is greater than that of Ar in the range of α
s
=0.1–0.7. The hystereses are detected for the N2 isotherm in p/p
o=0.1–0.3 at 77.4 K and for the Ar isotherm in p/p
o=3×10−4–2×10−3 at 87.3 K. However, it is difficult to explain the hysteresis phenomenon using differential adsorption energy. 相似文献
8.
Yu-Feng Hu Xian-Ming Zhang Chuan-Wei Jin Xiao-Ming Peng 《Journal of solution chemistry》2010,39(12):1828-1844
Viscosities were measured for the ternary aqueous systems NaCl–mannitol(C6H14O6)–H2O, NaBr–mannitol–H2O, KCl–mannitol–H2O, KCl–glycine(NH2CH2COOH)–H2O, KCl–CdCl2–H2O, and their binary subsystems NaCl–H2O, KCl–H2O, NaBr–H2O, CdCl2–H2O, mannitol–H2O, and glycine–H2O at 298.15 K. A powerful new approach is presented for theoretical modeling of the viscosity of multicomponent solutions
in terms of the properties of their binary solutions. In this modeling, the semi-ideal solution theory was used to associate
the solvation structure formed by each ion and its first solvation shell in a binary solution with the solvation structure
of the same ion and its first solvation shell in multicomponent solutions. Then, the novel mechanism proposed by Omta et al.
(Science, 301:347–349, 2003) for the effect of a single electrolyte on the viscosity of water was extended to describe the influence of solute mixtures
on the viscosity of water, including electrolyte mixtures, nonelectrolyte mixtures, and mixtures of electrolytes with nonelectrolytes.
The established simple equation was verified by comparison with measured viscosities and viscosities reported in literature.
The agreements are very impressive. This formulation provides a powerful new approach for modeling this transport property
in solutions. It can stimulate further research in establishing a dynamical analogue to that formulated for the thermodynamics
of multicomponent solutions. It is also very important for the study of hydration of ions. 相似文献
9.
The solubility of d-metal halides in MCl2-M′Cl2-H2O systems with competitive complex formation at 25°C was discussed. The role of complex formation and hydration was traced.
As the stability constants become closer to each other, the salting-in regions in the crystallization braches of both chlorides
disappear.
Original Russian Text I.V. Zamyatin, M.Yu. Skripkin, 2007, published in Zhurnal Obshchei Khimii, 2007, Vol. 77, No. 2, pp.
252–259. 相似文献
10.
At a certain concentration of NH4F, the solid allocyric solutions of the (C4H9)4NF−NH4F−H2O system stratify into two liquid phases in the process of melting. The mutual solubility of the liquids decreases at elevated
temperatures. The boundary surface of the stratification region was determined The solubility isotherms (27 and 30°C) of the
stratification region are investigated by the solubility method This relatively rare mutual sulubility of liquids (retrograde
solubility) is associated with clathrate formation in the liquid phase. Near the melting points of the solid clathrate solutions,
both in the liquid and solid phases the tetrabutylammonium cation evidently forms surrounding cavities bounded by water and
ammonium fluoride molecules linked by hydrogen bonds. The clathrate-like components of the solution are structurally compatible
with “water-like” and “organic” components, i.e., they are homogenizing components. At higher temperatures, the homogenizing
clathrate-like structures break down, and the structurally incompatible solution components stratify into two phases.
Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol 35, No. 6, pp. 122–128, November–December, 1994.
Translated by L. Smolina 相似文献
11.
Various model equations are available for representing the excess Gibbs energy properties (osmotic and activity coefficients)
of aqueous and other liquid mixed-electrolyte solutions. Scatchard’s neutral-electrolyte model is among the simplest of these
equations for ternary systems and contains terms that represent both symmetrical and asymmetrical deviations from ideal mixing
behavior when two single-electrolyte solutions are mixed in different proportions at constant ionic strengths. The usual form
of this model allows from zero to six mixing parameters. In this report we present an analytical method for transforming the
mixing parameters of neutral-electrolyte-type models with larger numbers of mixing parameters directly to those of models
with fewer mixing parameters, without recourse to the source data used for evaluation of the original model parameters. The
equations for this parameter conversion are based on an extension to ternary systems of the methodology of Rard and Wijesinghe
(J. Chem. Thermodyn. 35:439–473, 2003) and Wijesinghe and Rard (J. Chem. Thermodyn. 37:1196–1218, 2005) that was applied by them to binary systems. It was found that the use of this approach with a constant ionic-strength cutoff
of I≤6.2 mol⋅kg−1 (the NaCl solubility limit) yielded parameters for the NaCl+SrCl2+H2O and NaCl+MgCl2+H2O systems that predicted osmotic coefficients φ in excellent agreement with those calculated using the same sets of parameters whose values were evaluated directly from
the source data by least-squares, with root-mean-square differences of RMSE(φ)=0.00006 to 0.00062 for the first system and RMSE(φ)=0.00014 to 0.00042 for the second. If, however, the directly evaluated parameters were based on experimental data where
the ionic strength cutoff varied with the ionic-strength fraction, i.e., because they were constrained by isopiestic ionic
strengths (MgCl2+MgSO4+H2O) or solubility/oversaturation ionic strengths (NaCl+SrCl2+H2O and NaCl+MgCl2+H2O), then parameters converted by this approach assuming a constant ionic-strength cutoff yield RMSE(φ) differences about an order of magnitude larger than the previous case. This indicates that for an accurate conversion of
model parameters when the source model is constrained with variable ionic strength cutoffs, an extension of the parameter
conversion method described herein will be required. However, when the source model parameters are evaluated at a constant
ionic strength cuttoff, such as when source isopiestic data are restricted to ionic strengths at or below the solubility limit
of the less soluble component, or are Emf measurements that are commonly made at constant ionic strengths, then our method
yields accurate converted models.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users. 相似文献
12.
P. Ya. Tishchenko 《Russian Chemical Bulletin》2000,49(4):674-679
The buffer solution TRIS—TRIS·HCl−NaCl−H2O was studied in the 0–40 °C temperature region and ionic strength interval of (0.1–4)m (m is molality) by the e.m.f. method using two types of cells without liquid junction composed of platinum-hydrogen, silverchloride,
and sodium-glass electrodes. For temperatures of 5 and 15 °C and the (1–4)m concentration region, the osmotic coefficients of the TRIS·HCl−H2O solutions were measured by the isopiestic method. The results were processed in the framework of the Pitzer method, and
the parameters of interaction of the components of the buffer system were calculated. The associative character of the interactions
in the TRIS·HCl−H2O solution was shown.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 670–675, April, 2000. 相似文献
13.
Budrugeac P. Criado J. M. Gotor F. J. Popescu C. Segal E. 《Journal of Thermal Analysis and Calorimetry》2001,63(3):777-786
The heats of hydration reactions for MgCl2⋅4H2O and MgCl2⋅2H2O include two parts, reaction enthalpy and adsorption heat of aqueous vapor on the surfaces of magnesium chloride hydrates.
The hydration heat for the reactions MgCl2⋅4H2O+2H2O→MgCl2⋅6H2O and MgCl2⋅2H2O+2H2O→MgCl2⋅4H2O, measured by DSC-111, is –30.36 and –133.94 kJ mol–1,respectively. The adsorption heat of these hydration processes, measured by head-on chromatography method, is –13.06 and
–16.11 kJ mol–1, respectively. The molar enthalpy change for the above two reactions is –16.64 and –118.09 kJ mol–1, respectively. The comparison between the experimental data and the theoretical values for these hydration processes indicates
that the results obtained in this study are quite reliable.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
Summary. Calcium sulfate occurs in nature in form of three different minerals distinguished by the degree of hydration: gypsum (CaSO4·2H2O), hemihydrate (CaSO4·0.5H2O) and anhydrite (CaSO4). On the one hand the conversion of these phases into each other takes place in nature and on the other hand it represents
the basis of gypsum-based building materials. The present paper reviews available phase diagram and crystallization kinetics
information on the formation of calcium sulfate phases, including CaSO4-based double salts and solid solutions.
Uncertainties in the solubility diagram CaSO4–H2O due to slow crystallization kinetics particularly of anhydrite cause uncertainties in the stable branch of crystallization.
Despite several attempts to fix the transition temperatures of gypsum–anhydrite and gypsum–hemihydrate by especially designed
experiments or thermodynamic data analysis, they still vary within a range from 42–60°C and 80–110°C. Electrolyte solutions
decrease the transition temperatures in dependence on water activity.
Dry or wet dehydration of gypsum yields hemihydrates (α-, β-) with different thermal and re-hydration behaviour, the reason
of which is still unclear. However, crystal morphology has a strong influence.
Gypsum forms solid solutions by incorporating the ions HPO4
2−, HAsO4
2−, SeO4
2−, CrO4
2−, as well as ion combinations Na+(H2PO4)− and Ln3+(PO4)3−. The channel structure of calcium sulfate hemihydrate allows for more flexible ion substitutions. Its ion substituted phases
and certain double salts of calcium sulfate seem to play an important role as intermediates in the conversion kinetics of
gypsum into anhydrite or other anhydrous double salts in aqueous solutions. The same is true for the opposite process of anhydrite
hydration to gypsum. Knowledge about stability ranges (temperature, composition) of double salts with alkaline and alkaline
earth sulfates (esp. Na2SO4, K2SO4, MgSO4, SrSO4) under anhydrous and aqueous conditions is still very incomplete, despite some progress made for the systems Na2SO4–CaSO4 and K2SO4–CaSO4–H2O.
Corresponding author. E-mail: daniela.freyer@chemie.tu-freiberg.de
Received December 17, 2002; accepted January 10, 2003
Published online April 3, 2003 相似文献
15.
The solubility of boric acid [B] in LiCl, NaCl, KCl, RbCl, and CsCl was determined as a function of ionic strength (0–6 mol ⋅ kg−1) at 25 ∘C. The results were examined using the Pitzer equation
where [B]0 is the concentration of boric acid in water and [B] in solution, γB is the activity coefficient, νi is the number of ions (i), λBc, λBa are parameters related to the interaction of boric acid with cation c and anion a, ζB-a−c is related to the interaction of boric acid with both cation and anion and m is the salt molality. The literature values for the solubility of boric acid in a number of other electrolytes were also examined using the same equation. The results for the 2νcλBc+2νaλBa term (equal to the salting coefficient k
S) were examined in terms of the ionic interactions in the solutions. The solubility of boric acid in LiCl, NaCl, and KCl solutions is not a strong function of temperature and the results can be used over a limited temperature range (5–35 ∘C). Boric acid is soluble in the order SO4 > NO3 and F > Cl > Br > I in common cation solutions. In common anion salt solutions, the order is Cs > Rb > K > Na > Li > H and Ba > Sr > Ca > Mg. The results were examined using correlations of k
S with the volume properties of the ions. When direct measurements were not available, k
S and ζB-c−a were estimated from known values of λBc and λBa.The values of λBc, λBa, and ζB-a−c can be used to estimate the boric acid activity coefficients γB and solubility [B] in natural mixed electrolyte solutions (seawater and brines) using the more general Pitzer equation
相似文献
16.
Densities of solutions of tetramethyl-bis-urea (TMbU) or “Mebicarum” in H2O and D2O, with solute mole fraction concentrations (x
2) ranging up to 3.2 × 10−3, have been measured at 288.15, 298.15, 308.15 and 318.15 K using a precision vibrating-tube densimeter. The limiting apparent
molar volumes, V
φ,2
∞, and expansibilities, E
p, φ, 2
∞, of the solute have been calculated. The isotope effect δ V
φ,2
∞(H2O → D2O;T) is negative, monotonously decreases in magnitude with temperature and reverses sign at T ≈ 318 K. Water (H2O, D2O) and TMbU molecules in infinitely- and highly-dilute aqueous solutions form H(D)-bonded hydration complexes with a high packing density.
The hydration of TMbU should be treated as a superposition of two mechanisms, hydrophobic and hydrophilic, with the latter one predominating. 相似文献
17.
On the basis of conductometric measurements, empirical equations were derived that describe the temperature and concentration
dependences of the electrical conductance of Na2SeO3 solutions in ordinary and heavy water. The values of the equivalent conductance of the ions at infinite dilution were determined
in the temperature region 12 to 45 °C, as well as the kinetic parameters for ionic motion in the solutions. These parameters
were compared with respect to the solvent nature. The values of the effective ionic radii and ionic hydration numbers were
obtained.
The changes of Gibbs energy, entropy and enthalpy for the transition of ions from one quasi-equilibrium state to another were
calculated at different temperatures. According to the terms of Samoylov’s theory, Na+ and SeO32− ions in H2O and D2O were shown to be positively hydrated and stabilize the solvent structure, with this effect being more pronounced in D2O and increasing slightly with increasing temperature. 相似文献
18.
The heats of dissolution of tetramethyl-bis-carbamide (the pharmaceutical Mebicarum) in H2O and D2O were measured at 288.15, 298.15, and 318.15 K using a sealed microcalorimeter with an isothermal shell. The error of measurements
did not exceed 0.2%. The limiting molar enthalpies of dissolution Δsol
H
n
∞ and the H/D-isotope enthalpy effects of hydration δΔhydr
H
n
∞(H2O → D2O) were determined. Different effects of temperature on the pattern of variation of δΔ hydr
H
n
∞ were found: when T ≤ 315 K, this value is positive and decreases with T, while for T ≥ 315 K, hydration of tetramethyl-bis-carbamide upon replacement of H2O by D2O progressively becomes less endothermic.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 715–717, April, 2006. 相似文献
19.
Georgy G. Gospodinov Miluvka G. Stancheva 《Monatshefte für Chemie / Chemical Monthly》2002,81(1):1381-1386
The solubility isotherm of the system Lu2O3–SeO2–H2O was studied at 100°C. The compounds of the three-component system were identified by Schreinemakers’ method and chemical, derivatograph and X-ray phase analyses after separation in the pure state: Lu2(SeO3)3·4H2O and LuH(SeO3)2·2H2O. 相似文献
20.
Raman spectroscopy at 25 °C was performed to analyze speciation in quenched solutions after experiments on sodium tungstates
and sodium tungstate bronze dissolution at t=500 °C, p=1000 bar. The experiments were conducted under different oxidation-reduction conditions in sodium chloride solution media.
The spectra of the quenched solutions were different from those of the reference solutions of 0.02 mol⋅kg−1 W(VI) (H2O) in the pH range 2.3–7.2. Thermodynamic models were established and the fields of predominance of different isopolytungstate
species at 25–50 °C were determined. The experimental results of tungstate dissolution demonstrates that reduced tungstate
solutions may contain a significant amount of tungsten species with valence states lower than W(VI). 相似文献