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1.
Ternary mutual diffusion coefficients measured by Taylor dispersion method (D11, D22, D12, and D21) are reported for aqueous solutions of KCl + theophylline (THP) at T = 298.15 K at carrier concentrations from (0.000 to 0.010) mol · dm?3, for each solute. These diffusion coefficients have been measured having in mind a better understanding of the structure of these systems and the thermodynamic behavior of potassium chloride and theophylline in solution. For example, from these data it will be possible to make conclusions about the influence of this electrolyte in diffusion of THP and to estimate some parameters, such as the diffusion coefficient of the aggregate between KCl and THP.  相似文献   

2.
The apparent specific volumes and isentropic compressibilities have been determined for polyvinylpyrrolidone in aqueous solutions of sodium citrate by density and sound velocity measurements at T = (283.15 to 308.15) K at atmospheric pressure. The results show a positive transfer volume of PVP from an aqueous solution to an aqueous sodium citrate solution. For low concentrations of PVP, the apparent specific volumes of PVP in water increased along with an increase in the polymer mass fraction, while in aqueous sodium citrate solutions decreased along with an increase in the polymer mass fraction. For high concentrations of PVP, the apparent specific volumes of PVP in water and in aqueous sodium citrate solutions were independent of the polymer mass fraction. The apparent specific isentropic compressibility of PVP is negative at T = (283.15 and 288.15) K, which imply that the water molecules around the PVP molecules are less compressible than the water molecules in the bulk solutions. The positive values of apparent specific isentropic compressibility at T = (298.15, 303.15, and 308.15) K imply that the water molecules around the PVP molecules are more compressible than the water molecules in the bulk solutions. Finally, it was found that the apparent specific isentropic compressibility of PVP increases as the concentration of sodium citrate increases.  相似文献   

3.
Binary mutual diffusion coefficients (interdiffusion coefficients) of nickel chloride in water at T = 298.15 K and T = 310.15 K, and at concentrations between (0.000 and 0.100) mol · dm?3, using a Taylor dispersion method have been measured. These data are discussed on the basis of the Onsager–Fuoss and Pikal models. The equivalent conductance at infinitesimal concentration of the nickel ion in these solutions at T = 310.15 K has been estimated using these results. Through the same technique, ternary mutual diffusion coefficients (D11, D22, D12, and D21) for aqueous solutions containing NiCl2 and lactose, at T = 298.15 K and T = 310.15 K, and at different carrier concentrations were also measured. These data permit us to have a better understanding of the structure of these systems and the thermodynamic behaviour of NiCl2 in different media.  相似文献   

4.
This work reports individual activity coefficients of ions at T = 298.15 K in aqueous solutions obtained from voltage values of the respective half-cell ion-selective-electrode and a single-junction Ag–AgCl reference electrode, filled with different reference solutions at different concentrations. For potassium and chloride ions in KCl aqueous solutions, reference solutions of KCl, NaCl, or CsCl were used. For sodium and chloride ions in aqueous NaCl solutions, reference solutions of CsCl were used. Experimental runs were performed at molalities (1, 2, and 3) m of the reference solution. The concentration of the sample solution was increased, starting from around 1 · 10?3 m, up to the molality of the reference solution. The values of activity coefficients are calculated using the Henderson equation to estimate the liquid-junction potential. Results show that the ionic activity coefficients are independent of the nature and concentration of reference solution.  相似文献   

5.
The previous isopiestic investigations of HTcO4 aqueous solutions at T = 298.15 K are believed to be unreliable, because of the formation of a ternary mixture at high molality. Consequently, published isopiestic molalities for aqueous HTcO4 solutions at T = 298.15 K were completed and corrected. Binary data (variation of the osmotic coefficient and activity coefficient of the electrolyte in solution in the water) at T = 298.15 K for pertechnetic acid HTcO4 were determined by direct water activity measurements. These measurements extend from molality m = 1.4 mol · kg−1 to m = 8.32 mol · kg−1. The variation of the osmotic coefficient of this acid in water is represented mathematically. Density variations at T = 298.15 K are also established and used to express the activity coefficient values on both the molar and molal concentration scale. The density law leads to the partial molar volume variations for aqueous HTcO4 solutions at T = 298.15 K, which are compared with published data.  相似文献   

6.
Binary mutual diffusion coefficients measured by the Taylor dispersion method, for aqueous solutions of paracetamol (PA) at concentrations from (0.001 to 0.050) mol·dm−3 at T = 298.15 K, are reported. From the Nernst–Hartley equation and our experimental results, the limiting diffusion coefficient of this drug and its thermodynamic factors are estimated, thereby contributing in this way to a better understanding of the structure of such systems and of their thermodynamic behaviour in aqueous solution at different concentrations.  相似文献   

7.
Ternary mutual diffusion coefficients measured by Taylor dispersion method (D11, D22, D12, and D21) are reported for aqueous solutions containing isoniazid and different electrolytes (NaCl, NaOH, or HCl) at T = 298.15 K at different carrier concentrations. These diffusion coefficients have been measured having in mind a better understanding of the structure of these systems and the thermodynamic behaviour of isoniazid in different media. For example, it is possible to make conclusions about the influence of these electrolytes in diffusion of isoniazid, and to obtain information concerning the number of moles of each component transported per mole of the other component driven by its own concentration gradient.  相似文献   

8.
Isopiestic measurements have been carried out at the temperature 298.15 K for two saturated aqueous solutions: {H2O + BaCl2(sat) + NaCl + NH4Cl} saturated with barium chloride and {H2O + BaCl2(sat) + mannitol(sat) + NaCl + NH4Cl} saturated with barium chloride and mannitol. Taking sodium chloride (aq) as reference solutions, osmotic coefficients of the aqueous solutions were determined. The experimental results are well represented by the ideal-like solution model.  相似文献   

9.
The Jones–Dole viscosity B-coefficients for various mono-, di-, and tri-saccharides in water and in (0.5, 1.0, 2.0, and 3.0) mol · kg?1 aqueous solutions of sodium acetate have been determined at different temperatures, T = (288.15, 298.15, 308.15, and 318.15) K from viscosity data. Densities used to determine viscosities have been reported earlier. The viscosity B-coefficients of transfer, ΔtB, has been estimated for the transfer of saccharides from water to aqueous sodium acetate solutions. The positive ΔtB values were obtained in all cases and their magnitudes increase with the increase in concentration of sodium acetate. Pair, ηAB and higher order, ηABB viscometric interaction coefficients (using McMillan–Mayer theory), and dB/dT coefficients have also been determined. Activation Gibbs free energies and other related thermodynamic activation parameters of viscous flow have been determined using Feakin’s transition-state theory. These parameters have been discussed in terms of solute–solute and solute–solvent interactions occurring in these solutions.  相似文献   

10.
The apparent molar volumes and isentropic compressibility of glycine, l-alanine and l-serine in water and in aqueous solutions of (0.500 and 1.00) mol · kg?1 di-ammonium hydrogen citrate {(NH4)2HCit} and those of (NH4)2HCit in water have been obtained over the (288.15 to 313.15) K temperature range at 5 K intervals at atmospheric pressure from measurements of density and ultrasonic velocity. The apparent molar volume and isentropic compressibility values at infinite dilution of the investigated amino acids have been obtained and their variations with temperature and their transfer properties from water to aqueous solutions of (NH4)2HCit have also been obtained. The results have been interpreted in terms of the hydration of the amino acids. In the second part of this work, water activity measurements by the isopiestic method have been carried out on the aqueous solutions of {glycine + (NH4)2HCit}, {alanine + (NH4)2HCit}, and {serine + (NH4)2HCit} at T = 298.15 K at atmospheric pressure. From these measurements, values of vapour pressure, osmotic coefficient, activity coefficient and Gibbs free energy were obtained. The effect of the type of amino acids on the (vapour + liquid) equilibrium of the systems investigated has been studied. The experimental water activities have been correlated successfully with the segment-based local composition Wilson model. Furthermore, the thermodynamic behaviour of the ternary solutions investigated has been studied by using the semi-ideal hydration model and the linear concentration relations have been tested by comparing with the isopiestic measurements for the studied systems at T = 298.15 K.  相似文献   

11.
The apparent molar volume and apparent molar isentropic compressibility of solutions of sodium di-hydrogen phosphate (NaH2PO4) in (1-propanol + water) mixed-solvent media with alcohol mass fractions of 0.00, 0.05, 0.10, and 0.15 are reported over the range of temperature (283.15 to 303.15) K at 5 K intervals. The results were fitted to a Redlich–Mayer type equation from which the apparent molar volume and apparent molar isentropic compressibility of the solutions at the infinite dilution were also calculated at the working temperature. The results show a positive transfer volume of NaH2PO4 from an aqueous solution to an aqueous 1-propanol solution. The apparent molar isentropic compressibility of NaH2PO4 in aqueous 1-propanol solutions is negative and it increases with increasing the concentration of NaH2PO4, 1-propanol, and temperature. Electrical conductivity and refractive index of the solutions are also studied at T = 298.15 K. The effects of the electrolyte concentration and relative permittivity of the medium on the molar conductivity were also investigated.  相似文献   

12.
Ternary mutual diffusion coefficients (D11, D22, D12 and D21) measured by the Taylor dispersion method are reported for aqueous solutions of {levodopa (l-dopa) + HCl} solutions at 25 °C and HCl concentrations up to 0.100 mol · dm−3. The coupled diffusion of l-dopa (1) and HCl (2) is significant, as indicated by large negative cross-diffusion coefficients. D21, for example, reaches values that are larger than D11, the main coefficient of l-dopa. Combined Fick and Nernst–Planck equations are used to analyze the proton coupled diffusion of l-dopa and HCl in terms of the binding of H+ ions to l-dopa and ion migration in the electric field generated by l-dopa and HCl concentration gradients.  相似文献   

13.
The equilibrium solubility of sodium 2-naphthalenesulfonate in binary (sodium chloride + water), (sodium sulfate + water), and (ethanol + water) solvent mixtures was measured at elevated temperatures from (278.15 to 323.15) K using a steady-state method. With increasing temperatures, the solubility increases in aqueous solvent mixtures. The results of these results were regressed by a modified Apelblat equation. The dissolution entropy and enthalpy determined using the method of the least-squares and the change of Gibbs free energy calculated with the values of ΔdiffSo and ΔdiffHo at T = 278.15 K.  相似文献   

14.
Electrochemical cells with two ion-selective electrodes against a single-junction reference electrode were used to obtain the activity coefficients of glycine in aqueous electrolyte solutions. Activity coefficient data were presented for {H2O  +  KCl (mS)  +  glycine (mA)}, and {H2O  +  NaCl (mS)  +  glycine (mA)} atT =  298.15 K and T =  308.15 K, respectively. The results show that the presence of an electrolyte and the nature of its cation have a significant effect on the activity coefficient of glycine in aqueous electrolyte solutions and, in turn, on the method of separation from its culture media. The results of the mean ionic activity coefficients of KCl were compared with those values reported in the literature, which were obtained by the isopiestic method. It was found that the method applied in this study provides accurate activity coefficient data. The effect of temperature on the mean ionic activity coefficient of NaCl in presence of glycine was also investigated.  相似文献   

15.
The solubility of anthracene was measured in pure water and in sodium chloride aqueous solution (salt concentration, m/mol · kg?1 = 0.1006, 0.5056, and 0.6082) at temperatures between (278 and 333) K. Solubility of anthracene in pure water agrees fairly well with values reported in earlier similar studies. Solubility of anthracene in sodium chloride aqueous solutions ranged from (6 · 10?8 to 143 · 10?8) mol · kg?1. Sodium chloride had a salting-out effect on the solubility of anthracene. The salting-out coefficients did not vary significantly with temperature over the range studied. The average salting-out coefficient for anthracene was 0.256 kg · mol?1.The standard molar Gibbs free energies, ΔtrG°, enthalpies, ΔtrH°, and entropies, ΔtrS°, for the transfer of anthracene from pure water to sodium chloride aqueous solutions were also estimated. Most of the estimated ΔtrG° values were positive [(20 to 1230) J · mol?1]. The analysis of the thermodynamic parameters shows that the transfer of anthracene from pure water to sodium chloride aqueous solution is thermodynamically unfavorable, and that this unfavorable condition is caused by a decrease in entropy.  相似文献   

16.
The solubility and the density in the aqueous ternary system (Li2SO4 + MgSO4 + H2O) at T = 308.15 K were determined by the isothermal evaporation. Our experimental results permitted the construction of the phase diagram and the plot of density against composition. It was found that there is one eutectic point for (Li2SO4 · H2O + MgSO4 · 7H2O), two univariant curves, and two crystallization regions corresponding to lithium sulphate monohydrate (Li2SO4 · H2O) and epsomite (MgSO4 · 7H2O). The system belongs to a simple co-saturated type, and neither double salts nor solid solution was found. Based on the Pitzer ion-interaction model and its extended HW models of aqueous electrolyte solution, the solubility of the ternary system at T = 308.15 K has been calculated. The predicted solubility agrees well with the experimental values.  相似文献   

17.
Diffusion coefficients of the Fe2(SO4)3)/water system at T = 298.15 K and at concentrations between 0.050 mol · dm−3 and 0.200 mol · dm−3 have been measured, using a conductimetric cell and an automatic apparatus to follow diffusion. The cell uses an open-ended capillary method. A conductimetric technique is used to follow the diffusion process by measuring the resistance of a solution inside the capillaries at recorded times. These data are discussed on the basis of the Onsager–Fuoss model. The diffusion of Fe2(SO4)3 is clearly affected by the Fe (III) hydrolysis. These data permit us to have a better understanding of the structure of such systems and the thermodynamic behaviour of ferric sulphate in different media.  相似文献   

18.
We determined apparent molar volumes V? at 298.15 ? (T/K) ? 368.15 and apparent molar heat capacities Cp,? at 298.15 ? (T/K) ? 393.15 for aqueous solutions of HIO3 at molalities m from (0.015 to 1.0) mol · kg?1, and of aqueous KIO3 at molalities m from (0.01 to 0.2) mol · kg?1 at p = 0.35 MPa. We also determined V? at the same p and at 298.15 ? (T/K) ? 368.15 for aqueous solutions of KI at m from (0.015 to 7.5) mol · kg?1. We determined Cp,? at the same p and at 298.15 ? (T/K) ? 393.15 for aqueous solutions of KI at m from (0.015 to 5.5) mol · kg?1, and for aqueous solutions of NaIO3 at m from (0.02 to 0.15) mol · kg?1. Values of V? were determined from densities measured with a vibrating-tube densimeter, and values of Cp,? were determined with a twin fixed-cell, differential temperature-scanning calorimeter. Empirical functions of m and T were fitted to our results for each compound. Values of Ka, ΔrHm, and ΔrCp,m for the proton ionization reaction of aqueous HIO3 are calculated and discussed.  相似文献   

19.
Electrochemical cells with two ion-selective electrodes, a cation ion-selective electrode against an anion ion-selective electrode, were used to measure the activity coefficient of amino acids in aqueous electrolyte solutions. Activity coefficient data were measured for (H2O + NaBr + glycine) and (H2O + NaBr + l-valine) at T=298.15 K. The maximum concentrations of sodium bromide, glycine, and l-valine were (1.0, 2.4, and 0.4) mol · kg−1, respectively. The results show that the presence of an electrolyte and the nature of both the cation and the anion of the electrolyte have significant effects on the activity coefficients of amino acid in aqueous electrolyte solutions.  相似文献   

20.
Apparent molar volumes Vϕ and apparent molar heat capacities Cp,ϕ were determined at the pressure 0.35 MPa for aqueous solutions of magnesium nitrate Mg(NO3)2 at molalities m = (0.02 to 1.0) mol · kg−1, strontium nitrate Sr(NO3)2 at m = (0.05 to 3.0) mol · kg−1, and manganese nitrate Mn(NO3)2 at m = (0.01 to 0.5) mol · kg−1. Our Vϕ values were calculated from solution densities obtained at T = (278.15 to 368.15) K using a vibrating-tube densimeter, and our Cp,ϕ values were calculated from solution heat capacities obtained at T = (278.15 to 393.15) K using a twin fixed-cell, differential, temperature-scanning calorimeter. Empirical functions of m and T were fitted to our results, and standard state partial molar volumes and heat capacities were obtained over the ranges of T investigated.  相似文献   

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