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1.
The equilibrium constants of the 1:1 NpO2+/benzoate complex were determined by spectrophotometric titrations at variable temperatures (T = 283 to 343 K) and the ionic strength of 1.05 mol · kg−1. The enthalpy of complexation at T = 298 K was determined by microcalorimetric titrations. Similar to other monocarboxylates, benzoate forms a weak complex with NpO2+ and the complexation is strengthened as the temperature is increased. The complexation is endothermic and is entropy-driven. The enhancement of the complexation at elevated temperatures is primarily attributed to the increasingly larger entropy gain when the water molecules are released from the highly-ordered solvation spheres of NpO2+ and benzoate to the bulk solvent where the degree of disorder is higher at higher temperatures. The spectroscopic features of the Np(V)/benzoate system, including the effect of temperature on the absorption bands, are discussed in terms of ligand field splitting and a thermal expansion mechanism.  相似文献   

2.
A quantitative understanding of the mode of interaction of drugs with target proteins provides a guide for the synthesis of new drug molecules. The binding of the antibiotic drug oxytetracycline with serum albumin has been studied by a combination of isothermal titration calorimetry (ITC), differential scanning calorimetry (DSC), steady-state and time-resolved fluorescence spectroscopy, and circular dichroism spectroscopy. The values of the binding constant (K), enthalpy change (ΔH), entropy (ΔS), and stoichiometry of binding have been determined along with the associated conformational changes in the protein. Oxytetracycline binds to bovine serum albumin with a 1:1 stoichiometry and with a weakly temperature dependent association constant of 1.8 · 104 at T = 298.15 K. The effect of ionic strength, tetrabutylammonium bromide, and sucrose on the thermodynamic parameters obtained from ITC and DSC measurements indicate involvement of predominantly ionic and hydrophobic interactions with a minor hydrogen bonding contribution in the drug-protein complexation. The DSC results on the binding of oxytetracycline with bovine serum albumin in the absence and presence of these additives provide quantitative information on the effect of drugs on the stability of bovine serum albumin, and suggest preferential complexation of one of the domains of the protein. The results further indicate that the drug occupies binding site II on bovine serum albumin.  相似文献   

3.
An extensive study of the tin(II)/phytate (Phy) system was carried out in NaNO3(aq), at different ionic strengths (0.10  I/mol · L−1  1.00) and temperatures (278.15  T/K  328.15), by potentiometric and voltammetric techniques. The stability and formation enthalpy changes of six SnHqPhy species were determined. To better characterise this system, some potentiometric titrations were also carried out in mixed ionic media (NaNO3(aq) + NaCl(aq) and NaNO3(aq) + NaF(aq)) at total ionic strength I = 1.00 mol · L−1. The formation of some ternary mixed SnHqPhyCl and SnHqPhyF species (charges omitted for simplicity) was found. The formation enthalpies of the complex species were calculated, at I = 0.40 mol · L−1 in NaNO3(aq), by the dependence of stability constants on temperature obtained by potentiometric titrations, in the range 278.15  T/K  328.15. The complex formation process is endothermic, and the main contribution to tin(II) complexation by phytate is entropic in nature. For example, for the SnPhy species we have, at T = 298.15 K and I = 0.40 mol · L−1 in NaNO3(aq): ΔH = 57.7 ± 2.8 kJ mol · L−1, ΔG = −99.9 ± 1.7 kJ mol · L−1, and TΔS = 158 ± 3 kJ mol · L−1. The ionic strength dependence of the formation constants of the simple tin(II)/phytate species, was modelled by the Debye–Hückel and the SIT approaches. The sequestering ability of phytate towards tin(II) was evaluated by calculating the pL0.5 values (i.e., the total ligand concentration necessary to bind 50% of cation present in trace) at different ionic strengths, ionic media, and pH. The sequestering ability increases with increasing the pH, whilst it decreases with increasing the ionic strength (the same behaviour shown by the stability constants). Moreover, taking into account the different sequestering ability of phytate towards tin(II) in the different ionic media, the trend: pL0.5 = 5.70 (in NaNO3(aq) + NaF(aq)) > pL0.5 = 5.16 (in NaNO3(aq) + NaCl(aq)) > pL0.5 = 4.86 (in NaNO3(aq)) was observed at pH 8.1 and I = 1.00 mol · L−1. This is due to the presence of a second ligand (Cl or F) that stabilizes the complex species with the formation of ternary complex species. Some empirical relationships were also found.  相似文献   

4.
《Comptes Rendus Chimie》2007,10(8):742-747
A [4Fe–4S]1+ cluster-containing protein activates 2-hydroxyisocaproyl-CoA dehydratase by an ATP-driven electron transfer. The activator has been proposed to change its conformation by MgATP similarly to nitrogenase Fe-protein. Iron chelation by bathophenanthroline removed the reduced [4Fe–4S]1+ cluster from the activator in an ATP-dependent manner (rate, v = 0.128 ± 0.004 min−1; Km = 21 ± 1 μM); with ADP no chelation was observed (v < 0.001 min−1). Chelation of the oxidised [4Fe–4S]2+ cluster occurred faster with ADP (v = 0.34 ± 0.05 min−1) than with ATP (v = 0.132 ± 0.005 min−1). The data indicate that reduction of the activator and binding of ATP induce conformational changes necessary to transfer the electron to the dehydratase. Interaction of both proteins promotes ATP hydrolysis (Km = 0.5 ± 0.1 μM).  相似文献   

5.
New luminescent mononuclear and dinuclear copper(II) (S = 1/2) complexes [Cu(HL)(H2O)2](ClO4)2 (1a) and [Cu2(HL)2(μ-SO4)2]·2H2O (1b) were synthesized with the acyclic tridentate pyridine-2-carboxaldehyde-2-pyridylhydrazone ligand, HL (1). Interestingly, the mononuclear complex 1a can be converted into the disulfate bridged dimeric copper(II) complex 1b by passing freshly prepared SO2 through the basic medium. On excitation at 290 nm, the ligand fluoresces at 364 nm due to an intraligand 1(π–π1) transition. Upon complexation with copper(II), the emission peak is slightly blue shifted (356 nm, F/F0 0.76 for 1a and 354 nm, F/F0 0.89 for 1b) with a little quenching in the emission intensity. The association constants (Kass (5.06 ± 0.004) × 104 for 1a and Kass (5.46 ± 0.006) × 104 for 1b at 298 K) and the thermodynamic parameters have been determined by UV–Vis spectroscopy. The molecular structure of the complex 1b (Cu?Cu 4.456 Å) has been determined by single crystal X-ray diffraction studies. The complex 1b exhibits a strong interaction towards DNA as revealed from the Kb (intrinsic binding constant) 6.3 × 104 M?1 and Ksv (Stern–Volmer quenching constant) 2.93 values.  相似文献   

6.
Experimental air–liquid interfacial tension data and density data are presented for three 1-Cn-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphates (FAP), [CnMIM][(C2F5)3PF3], with n = 2, 4, and 6, measured at atmospheric pressure in the temperature range from 267 K to 360 K using the Krűss K100MK2 tensiometer. The accuracy of the surface tension measurements was checked by employing the Wilhelmy plate and the du Noüy ring methods in parallel. The combined standard uncertainty associated with the Wilhelmy plate method is estimated to be ±0.1 mN · m−1. The density data were obtained using buoyancy method with an estimated standard uncertainty less then ±0.4 kg · m−3 (3 · 10−4ϱ). The chloride anions decrease the density of the tris(pentafluoroethyl)trifluorophosphates of interest up to six times more effectively than they decrease the density of the imidazolium based tetrafluoroborates. A QSPR analysis of the surface tension of imidazolium based ionic liquids with BF4, TFA, DCA, FAP, NTf2, and PF6 anions indicates, that the FAP ionic liquids fit well into the analyzed group of imidazolium based ionic liquids while those having hexafluorophosphate anion show anomalously high deviations of the experimental surface tension from the values predicted by the QSPR model.  相似文献   

7.
N. Xaba  D. Jaganyi 《Polyhedron》2009,28(6):1145-1149
Hydroboration reactions of 4-octene with HBBr2 · SMe2, HBCl2 · SMe2 and H2BBr · SMe2 in CH2Cl2 were studied as function of concentration and temperature and compared with those of 1-octene. On average, hydroboration with dihaloborane proceeded 16 times slower for 4-octene than for 1-octene. In the case of the reactions with the monohaloborane, this factor is halved. This can be explained by the difference in the relative rates of dissociates of Me2S from the dihaloborane and a monohaloborane complex, respectively. The reactions involving H2BBr · SMe2 also exhibited a k?2 value, an indication of the presence of a parallel reaction, most likely a rearrangement process facilitating isomerization by way of a π-complex. The moderate ΔH values accompanied by small ΔS values (94 ± 4 kJ mol?1, ?3 ± 13 J K?1 mol?1 for HBBr2 · SMe2; 93 ± 1 kJ mol?1, ?17 ± 4 J K?1 mol?1 for HBCl2 · SMe2 and in the case of H2BBr · SMe2, 90 ± 13 kJ mol?1, +12 ± 44 J K?1 mol?1 and 83 ± 13 kJ mol?1, ?24 ± 45 J K?1 mol?1, respectively, for the k2 and k?2 processes) imply a process that is dissociatively dominated, with the overall mode of activation being interchange dissociative (Id).  相似文献   

8.
Electron paramagnetic resonance (EPR) study of Cu2+ doped bis (glycinato) Mg (II) monohydrate single crystals is carried out at room temperature. Copper enters the lattice substitutionally and is trapped at two magnetically inequivalent sites. The observed spectra are fitted to a spin-Hamiltonian of rhombic symmetry with the following values of the parameters: Cu2+ (I), gx = 2.1577 ± 0.0002, gy = 2.2018 ± 0.0002, gz = 2.3259 ± 0.0002, Ax = (87 ± 2) × 10?4 cm?1, Ay = (107 ± 2) × 10?4 cm?1, Az = (141 ± 2) × 10?4 cm?1; Cu 2+ (II), gx = 2.1108 ± 0.0002, gy = 2.1622 ± 0.0002, gz = 2.2971 ± 0.0002, Ax = (69 ± 2) × 10?4 cm?1, Ay = (117 ± 2) × 10?4 cm?1and Az = (134 ± 2) × 10?4 cm?1. The ground state wave function of the Cu2+ ion in this lattice is evaluated to be predominantly |x2 ? y2. The g-factor anisotropy is also calculated and compared with the experimental value. With the help of the optical absorption study, the nature of bonding in the complex is discussed.  相似文献   

9.
《Polyhedron》2005,24(16-17):2102-2107
Four complexes of M(NO3)2(4NOPy-OMe)2, (4NOPy-OMe = 4-(N-tert-butyloxylamino)-2-(methoxymethylenyl)pyridine, and M = MnII, 1; CoII, 2; NiII, 3; CuII, 4), were prepared and fully characterized. X-ray single crystal analysis reveals that four complexes are isostructural. The molecular structures are distorted octahedral in which the methoxy oxygen atoms coordinate to the metal ion by trans-configuration while the pyridyl nitrogen atoms and the nitrate oxygen atoms coordinate by cis-configuration. The magnetic properties of all complexes were investigated by SQUID magneto/susceptometry. Temperature dependence of the molar magnetic susceptibilities in the temperature range of 2–300 K indicated that the magnetic coupling between aminoxyl radicals and metal ion was antiferromagnetic in the complex 1 and were ferromagnetic in the complexes 24. The quantitative analysis based on the spin Hamiltonian, H = −2J(S1SM + SMS2) yielded the best fit as J/kB = −13.4 ± 0.1 K, g = 1.94 ± 0.002, and θ = −0.78 ± 0.02 K for the complex 1, J/kB = 48.7 ± 2.1 K, g = 2.07 ± 0.02, and θ = −2.83 ± 0.41 K for the complex 3 (the data in the temperature range 300–50 K were used), and J/kB = 57.0 ± 1.2 K, g = 2.002 ± 0.004, and θ = −9.8 ± 0.1 K for the complex 4.  相似文献   

10.
In this Letter we report the results of the measurements of the rate coefficients for thermal attachment to several perfluoroethers namely perfluorodiglyme (C6F14O3), perfluorotriglyme (C8F18O4), perfluoropolyether (CF3–(OCF(CF3)CF2)n–(OCF2)m–OCF3) and perfluorocrownether ((C2F4O)5). Rate coefficients were obtained under thermal conditions in the temperature range 298–378 K. The increase of the rates with temperature follows the Arrhenius law and the activation energies have been obtained from the slope of the ln(k) vs. 1/T. The respective values of the rate coefficients (at 298 K) and activation energies are as follows: 7.7 ± 1.2 × 10?11 cm3 s?1 (0.18 ± 0.005 eV), 6.7 ± 2.1 × 10?11 cm3 s?1 (0.25 ± 0.004 eV), 2.1 ± 0.2 × 10?10 cm3 s?1 (0.16 ± 0.010 eV), 3.1 × 10?11 cm3 s?1 (0.27 ± 0.003 eV) for C6F14O3, C8F18O4, CF3–(OCF(CF3)CF2)n–(OCF2)m–OCF3 and (C2F4O)5.  相似文献   

11.
To obtain reliable thermodynamic data for Na2S(s), solid-state EMF measurements of the cell Pd(s)|O2(g)|Na2S(s), Na2SO4(s)|YSZ| Fe(s), FeO(s)|O2(g)ref| Pd(s) were carried out in the temperature range 870 < T/K < 1000 with yttria stabilized zirconia as the solid electrolyte. The measured EMF values were fitted according to the equation Efit/V (±0.00047) = 0.63650  0.00584732(T/K) + 0.00073190(T/K) ln (T/K). From the experimental results and the available literature data on Na2SO4(s), the equilibrium constant of formation for Na2S(s) was determined to be lg Kf(Na2S(s)) (±0.05) = 216.28  4750(T/K)−1  28.28878 ln (T/K). Gibbs energy of formation for Na2S(s) was obtained as ΔfG(Na2S(s))/(kJ · mol−1) (±1.0) = 90.9  4.1407(T/K) + 0.5415849(T/K) ln (T/K). By applying third law analysis of the experimental data, the standard enthalpy of formation of Na2S(s) was evaluated to be ΔfH(Na2S(s), 298.15 K)/(kJ · mol−1) (±1.0) = −369.0. Using the literature data for Cp and the calculated ΔfH, the standard entropy was evaluated to S(Na2S(s), 298.15 K)/(J · mol−1 · K−1) (±2.0) = 97.0.  相似文献   

12.
A kinetic spectrophotometric method for the determination of thiocyanate, based on its inhibitory effect on silver(I) catalyzed substitution of cyanide ion, by phenylhydrazine in hexacyanoferrate(II) is described. Thiocyanate ions form strong complexes with silver(I) catalyst which is used as the basis for its determination at trace level. The progress of reaction was monitored, spectrophotometrically, at 488 nm (λmax of [Fe(CN)5PhNHNH2]3?, complex) under the optimum reaction conditions at: 2.5 × 10?3 M [Fe(CN)6]4?, 1.0 × 10?3 M [PhNHNH2], 8.0 × 10?7 M [Ag+], pH 2.8 ± 0.02, ionic strength (μ) 0.02 M (KNO3) and temperature 30 ± 0.1 °C. A linear relationship obtained between absorbance (measured at 488 nm at different times) and inhibitor concentration, under specified conditions, has been used for the determination of [thiocyanate] in the range of 0.8–8.0 × 10?8 M with a detection limit of 2 × 10?9 M. The standard deviation and percentage error have been calculated and reported with each datum. A most plausible mechanistic scheme has been proposed for the reaction. The values of equilibrium constants for complex formation between catalyst–inhibitor (KCI), catalyst–substrate (Ks) and Michaelis–Menten constant (Km) have been computed from the kinetic data. The influence of possible interference by major cations and anions on the determination of thiocyanate and their limits has been investigated.  相似文献   

13.
A new Tb(III) dimer with an oxazoline-derivatized pyridine ligand, dimethyl-2,2′-(pyridine-2,6-diyl)bis(4,5-dihydrooxazole-4-carboxylate), has been isolated. This complex is highly luminescent and crystallizes in the triclinic P-1 space group with parameters a = 9.6167(2) Å, b = 11.6786(2) Å, c = 12.7548(3) Å, α = 70.026(1)°, β = 83.219(1)°, γ = 81.973(1)° and V = 1329.31(51)Å3. Solution speciation studies showed the formation of monomeric species with 1:1 and 2:1 ligand-to-metal ion stoichiometries with log β11 = 3.66 ± 0.41 and log β21 = 6.16 ± 0.37 for Eu(III) and log β11 = 3.56 ± 0.41 and log β21 = 6.21 ± 0.38 for Tb(III). The quantum yields of emission Φ and luminescence lifetimes τ of solutions with 2:1 stoichiometry were 26.4 ± 0.5% and 1.47 ± 0.06 ms for Eu(III) and 41.0 ± 1.3% and 1.87 ± 0.06 ms for Tb(III).  相似文献   

14.
《Polyhedron》2005,24(6):723-729
The mixed ligand complex [La(hfa)3(Phen)2] (I) was obtained by the interaction of La(hfa)3 and Phen; its composition does not depend on the stoichiometry of the reagents. According to the X-ray single crystal analysis data, complex I crystallizes in the monoclinic space group P21/n, with a = 13.583(3) Å, b = 16.959(3) Å, c = 18.860(4) Å, β = 94.71(3)° and Z = 4. The structure of I consists of isolated mononuclear molecules, the coordination number of La being 10. Thermal behaviour and composition of the vapor phase have been studied for I by thermal analysis and mass-spectrometry using a Knudsen cell. The mixed ligand complex I was found to sublime congruently in the temperature range 370–460 K: [La(hfa)3(Phen)2](s) = [La(hfa)3(Phen)](g) + Phen(g), ΔrH0(T) = 316.2 ± 1.8 kJ/mol.  相似文献   

15.
Microcalorimetry, spectrophotometry, and high-performance liquid chromatography (h.p.l.c.) have been used to conduct a thermodynamic investigation of the glutathione reductase catalyzed reaction {2 glutathionered(aq) + NADPox(aq)=glutathioneox(aq) + NADPred(aq)}. The reaction involves the breaking of a disulfide bond and is of particular importance because of the role glutathionered plays in the repair of enzymes. The measured values of the apparent equilibrium constant K for this reaction ranged from 0.5 to 69 and were measured over a range of temperature (288.15 K to 303.15 K), pH (6.58 to 8.68), and ionic strength Im (0.091 mol · kg−1 to 0.90 mol · kg−1). The results of the equilibrium and calorimetric measurements were analyzed in terms of a chemical equilibrium model that accounts for the multiplicity of ionic states of the reactants and products. These calculations led to values of thermodynamic quantities at T=298.15 K and Im=0 for a chemical reference reaction that involves specific ionic forms. Thus, for the reaction {2 glutathionered(aq) + NADPox3−(aq)=glutathioneox2−(aq) + NADPred4−(aq) + H+(aq)}, the equilibrium constant K=(6.5±4.4)·10−11, the standard molar enthalpy of reaction ΔrHom=(6.9±3.0) kJ · mol−1, the standard molar Gibbs free energy change ΔrGom=(58.1±1.7) kJ · mol−1, and the standard molar entropy change ΔrSom=−(172±12) J · K−1 · mol−1. Under approximately physiological conditions (T=311.15 K, pH=7.0, and Im=0.25 mol · kg−1 the apparent equilibrium constant K≈0.013. The results of the several studies of this reaction from the literature have also been examined and analyzed using the chemical equilibrium model. It was found that much of the literature is in agreement with the results of this study. Use of our results together with a value from the literature for the standard electromotive force Eo for the NADP redox reaction leads to Eo=0.166 V (T=298.15 K and I=0) for the glutathione redox reaction {glutathioneox2−(aq) + 2 H+(aq) + 2 e=2 glutathionered(aq)}. The thermodynamic results obtained in this study also permit the calculation of the standard apparent electromotive force E′o for the biochemical redox reaction {glutathioneox(aq) + 2 e=2 glutathionered(aq)} over a wide range of temperature, pH, and ionic strength. At T=298.15 K, I=0.25 mol · kg−1, and pH=7.0, the calculated value of E′o is −0.265 V.  相似文献   

16.
Heat capacities of 2,2-dimethyl-1,3-propanediol(CH3)2C(CH2OH)2 were measured in the temperature range between T =  13 K and T =  350 K using an adiabatic calorimeter. The compound underwent a first-order phase transition at T =  (314.5  ±  0.1) K. The enthalpy and the entropy of transition were (12.52  ±  0.02)kJ · mol  1and (39.81  ±  0.08)J · K  1· mol  1, respectively. Measurement of the fusion peak by d.s.c. showed that the purity of the sample was 0.9999 mass fraction and the entropy of fusion was 9.9 J · K  1· mol  1. Another first-order phase transition was observed at T =  (60.4  ±  0.1) K with the associated entropy change of (2.93  ±  0.05)J · K  1· mol  1. Heat capacities of two deuterated samples,(CH3)2C(CH2OD)2 and(CD3)2C(CD2OD)2 , were also measured and the results were compared with those on the natural compound. Possible mechanisms of the transition have been discussed from the isotope effects on the thermodynamic quantities associated with the transition. Standard thermodynamic functions of the compounds are tabulated.  相似文献   

17.
The molar heat capacities of GeCo2O4 and GeNi2O4, two geometrically frustrated spinels, have been measured in the temperature range from T=(0.5 to 400) K. Anomalies associated with magnetic ordering occur in the heat capacities of both compounds. The transition in GeCo2O4 occurs at T=20.6 K while two peaks are found in the heat capacity of GeNi2O4, both within the narrow temperature range between 11.4<(T/K)<12.2. Thermodynamic functions have been generated from smoothed fits of the experimental results. At T=298.15 K the standard molar heat capacities are (143.44 ± 0.14) J · K−1 · mol−1 for GeCo2O4 and (130.76 ± 0.13) J · K−1 · mol−1 for GeNi2O4. The standard molar entropies at T=298.15 K for GeCo2O4 and GeNi2O4 are (149.20 ± 0.60) J · K−1 · mol−1 and (131.80 ± 0.53) J · K−1 · mol−1 respectively. Above 100 K, the heat capacity of the cobalt compound is significantly higher than that of the nickel compound. The excess heat capacity can be reasonably modeled by the assumption of a Schottky contribution arising from the thermal excitation of electronic states associated with the CO2+ ion in a cubic crystal field. The splittings obtained, 230 cm−1 for the four-fold-degenerate first excited state and 610 cm−1 for the six-fold degenerate second excited state, are significantly lower than those observed in pure CoO.  相似文献   

18.
The low-temperature heat capacity of NiAl2O4 and CoAl2O4 was measured between T = (4 and 400) K and thermodynamic functions were derived from the results. The measured heat-capacity curves show sharp anomalies peaking at around T = 7.5 K for NiAl2O4 and at T = 9 K for CoAl2O4. The exact cause of these anomalies is unknown. From our results, we suggest a standard entropy for NiAl2O4 at T = 298.15 K of (97.1 ± 0.2) J · mol?1 · K?1 and for CoAl2O4 of (100.3 ± 0.2) J · mol?1 · K?1.  相似文献   

19.
The thermodynamic properties ofZn5(OH)6(CO3)2 , hydrozincite, have been determined by performing solubility and d.s.c. measurements. The solubility constant in aqueous NaClO4media has been measured at temperatures ranging from 288.15 K to 338.15 K at constant ionic strength (I =  1.00 mol · kg  1). Additionally, the dependence of the solubility constant on the ionic strength has been investigated up to I =  3.00 mol · kg  1NaClO4at T =  298.15 K. The standard molar heat capacity Cp, mofunction fromT =  318.15 K to T =  418.15 K, as well as the heat of decomposition of hydrozincite, have been obtained from d.s.c. measurements. All experimental results have been simultaneously evaluated by means of the optimization routine of ChemSage yielding an internally consistent set of thermodynamic data (T =  298.15 K): solubility constant log * Kps 00 =  (9.0  ±  0.1), standard molar Gibbs energy of formationΔfGmo {Zn5(OH)6(CO3)2 }  =  (  3164.6  ±  3.0)kJ · mol  1, standard molar enthalpy of formation ΔfHmo{Zn5(OH)6(CO3)2 }  =  (  3584  ±  15)kJ · mol  1, standard molar entropy Smo{Zn5(OH)6(CO3)2 }  =  (436  ±  50)J · mol  1· K  1and Cp,mo / (J · mol  1· K  1)  =  (119  ±  11)  +  (0.834  ±  0.033)T / K. A three-dimensional predominance diagram is introduced which allows a comprehensive thermodynamic interpretation of phase relations in(Zn2 +  +  H2O  +  CO2) . The axes of this phase diagram correspond to the potential quantities: temperature, partial pressure of carbon dioxide and pH of the aqueous solution. Moreover, it is shown how the stoichiometric composition{n(CO3) / n(Zn)} of the solid compoundsZnCO3 and Zn5(OH)6(CO3)2can be checked by thermodynamically analysing the measured solubility data.  相似文献   

20.
The interaction between the zwitterionic buffers (3-[N-bis(2-hydroxyethyl)amino]-2-hydroxy propane sulfonic acid, N-(2-actamido)-2-aminoethane sulfonic acid, and 3-[(1,1-dimethyl-2-hydroxyethyl)amino]-2-hydroxy propane sulfonic acid) with some divalent transition metal ions (CuII, NiII, CoII, ZnII, and MnII) were studied at different temperatures (298.15 to 328.15) K at ionic strength I = 0.1 mol · dm−3 NaNO3 and in the presence of 10%, 30%, and 50% (w/w) dioxene by using potentiometry. The thermodynamic stability constants were calculated as well as the free energy change for the 1:1 binary complexation. The protonation constants of the zwitterionic buffers were also determined potentiometrically under the above conditions.  相似文献   

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