Density, Viscosity and Refraction Index of Aqueous Solutions of 7-Hydroxycoumarin and Ethanol or 1-Propanol at Temperatures from 293.15 to 313.15 K

7-Hydroxycoumarin exhibits antioxidative, lipoxygenase inhibitive and anti-tumourigenic effects. Density and viscosity measurements have been carried out for the solutions of 7-hydroxycoumarin in mixture solvents of water and ethanol or 1-propanol at T = (293.15, 298.15, 303.15, 308.15 and 313.15) K. The measured data have been used to evaluate apparent molar volumes (V _? ), limiting apparent molar volumes ( $ V_{\phi }^{0} $ ), viscosity B-coefficients of the Jones–Dole equation and variation of B with temperature (dB/dT). The values of $ V_{\phi }^{0} $ and B-coefficients are positive and pass through their corresponding maxima at about 18 mol·kg^?1 ethanol molality and 20 mol·kg^?1 1-propanol molality, respectively. Besides, the values of $ V_{\phi }^{0} $ and B-coefficients decrease with increasing temperature. Molar refractive indices (R _D) of the ternary solutions at the temperature of 298.15 K have also been determined from measured refractive indices (n _D). There is an obvious increase of R _D with increasing molality of the solvent. These parameters have been interpreted in terms of solute–solvent interactions and structure making/breaking ability of components in the aqueous solution. The temperature and concentration dependences of the weak interactions in the solution systems have also been discussed.     

Conductivity Studies of Dilute Aqueous Solutions of Oxalic Acid and Neutral Oxalates of Sodium, Potassium, Cesium, and Ammonium from 5 to 35°C

Conductivity measurements of oxalic acid and neutral oxalates (disodium oxalate, dipotassium oxalate, dicesium, and diammonium oxalate) were performed on dilute aqueous solutions, c < 3 × 10^–3 mol-dm^–3, from 5 to 35°C. These data and those available from the literature were analyzed in terms of dissociation steps of oxalic acid, the Onsager conductivity equation for neutral oxalates, the Quint–Viallard conductivity equation for the acid, and the Debye–Hückel equation for activity coefficients, to give the limiting equivalent conductances of bioxalate anion ;(HC₂O₄ ^–) and oxalate anion (1/2C₂O₄ ^2–) and the corresponding dissociation constants K ₁ and K ₂.     

Apparent Molar Volumes of Aqueous Solutions of Magnesium Tetraborate from 283.15 to 363.15 K and 0.1 MPa

Densities for aqueous solutions of magnesium tetraborate MgB₄O₇(aq) at the molalities of (0.00556–0.03341) mol·kg^?1 were measured with an Anton Paar Digital vibrating-tube densimeter at temperature intervals of 5 K from 283.15 to 363.15 K and 0.1 MPa. Apparent molar volumes were obtained based on the experimental density data, and the 3D diagrams of the apparent molar volume (V _? ) of MgB₄O₇(aq) against temperature (T) and molality (m) were plotted. On the basis of the Vogel–Tamman–Fulcher equation, the coefficients of the correlation equation for densities of MgB₄O₇(aq) against temperature and molality were parameterized. According to the Pitzer ion-interaction model of the apparent molar volume, the temperature correlation equations of Pitzer single-salt parameters F(i,p,T)?=?a₀?+?a₁?×?T?+?a₂?×?T ²?+?a₃/T?+?a₄?×?ln(T)?+?a₅?×?T ³ (where T is temperature in Kelvin, a _i are model parameters) for MgB₄O₇ were obtained for the first time.     

Partial Molar Volume,Ionization, Viscosity and Structure of Glycine Betaine in Aqueous Solutions

Densities, partial molar volumes, and viscosities of aqueous solutions of betaine have been measured at 5, 10, 15, 20, 25, 30, 37, and 45 °C over the concentration range 0.05 to 5.0 mol⋅L⁻¹. The partial molar volumes show that betaine exists partly as a monohydrate and partly in its anhydrous form. The proportion of the anhydrous form increases with increasing temperature. Also, an associated form of betaine appears in concentrated betaine solutions, possibly with water as a bridging group. The significance of the viscosity B-coefficient is discussed. The signs of B _st, the increment of the viscosity B-coefficients arising from structural changes of water, are negative and the signs of dB/dT, the temperature derivative of B, are positive. These results show that betaine is a water structure breaker especially at lower temperatures, and this effect decreases to insignificance at higher temperatures. The ionization equilibria of betaine were investigated in aqueous 0.5 mol⋅L⁻¹ and 1.0 mol⋅L⁻¹ NaNO₃ at 5, 15, 25, and 37 °C by a potentiometric method. Using the least-square computer program SUPERQUAD, the complex forms are deduced to be betanium BH, bis(betanium) BHB, and bis(betaine) B₂ or bis(betaine)hydrate BH₂OB.     

An Aqueous Thermodynamic Model for the Solubility of Potassium Ferrate in Alkaline Solutions to High Ionic Strengths from 283.15 to 333.15 K

Potassium ferrate, K₂FeO₄(cr), has numerous promising environmental applications. An aqueous thermodynamic model applicable to high ionic strengths is essential for guiding its applications. In this study, a thermodynamic model is developed for the solubility of K₂FeO₄(cr) in aqueous alkali metal hydroxide solutions, from 283.15 to 333.15 K to high ionic strengths, up to saturation of KOH and NaOH, based on the Pitzer activity coefficient model for aqueous species. The solubility products for K₂FeO₄(cr) at infinite dilution in the temperature range from 283.15 to 333.15 K were obtained. Based on the thermodynamic solubility product of K₂FeO₄(cr) at 298.15 and its temperature dependence, in combination with thermodynamic properties for $ {\text{FeO}}_{4}^{2 - } $ FeO 4 2 ? and K⁺ from the literature, standard thermodynamic properties of K₂FeO₄(cr) at 298.15 K and 0.1 MPa (1 bar) are derived for the first time as follows: Δ_f G ⁰ = ?(896 ± 8) kJ·mol^?1, Δ_f H ⁰ = ?(1026 ± 4) kJ·mol^?1, and S ⁰ = (130 ± 17) J·mol^?1·K^?1. Using the above thermodynamic properties for K₂FeO₄(cr), the potential presence or preservation of K₂FeO₄(cr) in the Martian soils under the conditions relevant to Mars were quantitatively evaluated. Thermodynamic calculations pertaining to the Martian conditions indicate that the presence or preservation of K₂FeO₄(cr) as a strong oxidant in the Martian soils can be supported.     

Transfer Volumes of Small Peptides from Water to Aqueous Xylitol Solutions at 298.15 K

Densities have been measured by an oscillating-tube densimeter for aqueous solutions of glycylglycine and glycylglycylglycine in aqueous xylitol solutions with xylitol mass fractions ranging from 0 to 0.15 at 298.15 K. Apparent molar volumes and limiting partial molar volumes have been used to calculate the corresponding transfer volumes from water to different concentrations of xylitol + water mixtures. The results are interpreted in terms of the cosphere overlap model.     

The Relative Reduced Redlich-Kister and Herráez Equations for Correlating Viscosities of 1,4-Dioxane + Water Mixtures at Temperatures from 293.15 K to 323.15 K

Viscosity deviations from ideal mixing for 1,4-dioxane + water mixtures over the entire range of composition at temperatures of (293.15, 303.15 and 313.15) K and atmospheric pressure were calculated from experimental viscosity data presented in a previous work. The temperature range was extended to 323.15 K with data from the literature. This system exhibits very large positive deviations due to strong heteromolecular interactions and also due to size differences of the unlike molecules. The viscosity data as well as their corresponding relative functions were used to test the applicability of two correlative equations: the reduced Redlich-Kister equation and the recently proposed Herráez equation. These relative functions are important to reduce the effect of temperature and, consequently, to reveal the effects of different types of interactions. Their correlation abilities at different temperatures, and using different numbers of parameters, are discussed for the case of limited experimental data. Generally, good agreement between experimental and calculated data was obtained with both equations provided more than three parameters were employed.     

Densities,Excess Molar Volumes,and Thermal Expansion Coefficients of Aqueous Aminoethylethanolamine Solutions at Temperatures from 283.15 to 343.15 K

The densities of aqueous mixtures of aminoethylethanolamine (CAS #000111-41-1) were measured over the entire compositional range at temperatures of 283.15–343.15 K. The results of these measurements were used to calculate excess molar volumes and isobaric thermal expansion coefficients, and partial molar and apparent molar volumes and excess isobaric thermal expansion coefficients were subsequently derived. The excess molar volumes were correlated as a function of the mole fraction using the Redlich–Kister equation. Temperature dependences of the Redlich–Kister coefficients are also presented. The partial molar volumes at infinite dilution of AEEA in water were determined using two different methods. In addition, the solution density was correlated using a Joubian–Acree model. Aqueous solutions of AEEA exhibit similar properties to the aqueous solutions of other alkanolamines (like monoethanolamine) used in acid gas sweetening.     

Conductivities of Several Ternary Electrolyte Solutions and Their Binary Subsystems at 293.15, 298.15, and 303.15 K

Conductivities were measured for the ternary systems NaNO₃–KNO₃–H₂O, NaCl–BaCl₂–H₂O, NaCl–LaCl₃–H₂O, and their binary subsystems NaNO₃–H₂O, KNO₃–H₂O, NaCl–H₂O, BaCl₂–H₂O, and LaCl₃–H₂O at (293.15, 298.15 and 303.15) K. The results were used to verify the generalized Young’s rule and the semi-ideal solution theory. Comparison of the results shows that the average relative differences between the predicted and measured conductivities are ≤4.2×10⁻³ for NaNO₃–KNO₃–H₂O, ≤4.6×10⁻³ for NaCl–BaCl₂–H₂O, and ≤8.9×10⁻³ for NaCl–LaCl₃–H₂O, indicating that the generalized Young’s rule and the semi-ideal solution theory can provide good predictions for the conductivity of mixed electrolyte solutions in terms of the data from their binary subsystems.     

Volumetric Properties of Aqueous Solutions of L-Glutamic Acid and Magnesium-L-Glutamate

Densities of aqueous solutions of L-glutamic acid and magnesium-L-glutamate were determined from T=288.15 to 333.15 K at 5 K temperature intervals. The measured densities were used to evaluate the apparent molar volumes, V _2,φ (m,T), the cubic expansion coefficients, α(m,T), and the changes of isobaric heat capacities with respect to pressure, (∂ C _p /∂ p) _T,m . They were qualitatively correlated with changes in the structure of water that occur when L-glutamic acid or magnesium-L-glutamate are present.     

Re-evaluation of the First and Second Stoichiometric Dissociation Constants of Oxalic Acid at Temperatures from 0 to 60 °C in Aqueous Oxalate Buffer Solutions with or without Sodium or Potassium Chloride

Equations were developed for the calculation of the first stoichiometric (molality scale) dissociation constant (K _m1) of oxalic acid in buffer solutions containing oxalic acid, potassium hydrogen oxalate, and potassium chloride from the determined thermodynamic values of this dissociation constant (K _a1) and the molalities of the components in the solutions. Similar equations were also developed for the second stoichiometric dissociation constant (K _m2) of this acid in buffer solutions containing sodium or potassium hydrogen oxalate, oxalate and chloride. These equations apply at temperatures from 0 to 60 °C up to ionic strengths of 1.0 mol⋅kg⁻¹ and they have been based on single-ion activity coefficient equations of the Hückel type. For the equations for K _m1, the activity parameters of oxalate species and the K _a1 values were determined at various temperatures from the Harned cell data of a recent tetroxalate buffer paper (Juusola et al., J. Chem. Eng. Data 52:973–976, 2007). By using the resulting equations for K _m1, the activity parameters of oxalate species for K _m2 and the K _a2 values were then determined from the new Harned cell data and from those of Pinching and Bates (J. Res. Natl. Bur. Stand. (U.S.) 40:405–416, 1948) for solutions of sodium or potassium oxalates with NaCl or KCl. The resulting simple equations for calculation of K _m1 and K _m2 for oxalic acid were tested with all important thermodynamic data available in the literature for this purpose. The equations for ln (K _a1) and ln (K _a2) are of the form ln (K _a)=a+b(t/°C)+c(t/°C)². The coefficients for ln (K _a1) are the following: a=−2.8737, b=0.000159, and c=−0.00009. The corresponding coefficients for ln (K _a2) are −9.6563, −0.003059, and −0.000125, respectively. The new activity coefficient equations were used to evaluate the pH values of the tetroxalate buffer solution (i.e., of the 0.05 mol⋅kg⁻¹ KH₃C₄O₈ solution) for comparison with the pH values recommended by IUPAC at temperatures from 0 to 60 °C and to develop a new two-component oxalate pH buffer of 0.01 mol⋅kg⁻¹ KHC₂O₄+0.05 mol⋅kg⁻¹ Na₂C₂O₄ for which pH values are given from 0 to 60  °C. Values of p(m _H) calculated from these equations are tabulated for these buffers as well as for buffer solutions with KCl and KH₃C₄O₈ as the major component and minor component, respectively. Tables of p(m _H) are also presented for 0.001 mol⋅kg⁻¹ KHC₂O₄+0.005 mol⋅kg⁻¹ Na₂C₂O₄ solutions in which KCl is the supporting electrolyte.     

The Enthalpies of Solution of L-cysteine, L-serine and L-asparagine in Aqueous Solutions of Some Alcohols at 298.15 K

Heats of solution, Δ_sol H _m , of L-cysteine, L-serine and L-asparagine amino acids have been measured at different concentrations of aqueous ethanol, propanol and 2-propanol at 298.15 K using solvation calorimetry. These data are compared with the results reported earlier for L-alanine in ethanol. The enthalpic coefficients, h _xy , of the solute-organic cosolvent pair interaction in water have been obtained from the McMillan-Mayer approach and the data have been interpreted in terms of various interactions and changes in solvent structure.     

Solubility of Argon and Nitrogen in Aqueous Solutions of Dodecyltrimethylammonium Bromide (DTAB) from 283.15 to 298.15 K and 101325 Pa Partial Pressure of Gas

The solubility of nitrogen and argon in aqueous solutions of dodecyltrimethylammonium bromide (DTAB) were measured, using the drop pressure method, at temperatures between (283.15 and 298.15) K and partial pressure of 101325 Pa of gas in an instrument specially developed for this purpose. The gas solubility was calculated as Henry’s constant. The solubilities of argon and of nitrogen increase linearly with DTAB concentration and decrease as the temperature increases. Experimental results show that the increase in the solubility of argon and nitrogen in the DTAB micelles is between 59.0 and 83.5 higher than the solubility in pure water, reflecting the ability of DTAB micelles to increase the solubility of non-polar gases in water.     

Volumetric Properties of l-Alanine and l-Serine in Aqueous N,N-Dimethylformamide Solutions at 298.15 K

The densities of l-alanine and l-serine in aqueous solutions of N,N-dimethylformamide (DMF) have been measured at 298.15 K with an Anton Paar Model 55 densimeter. Apparent molar volumes $ (V_{\phi } ) $ ( V ? ) , standard partial molar volumes $ (V_{\phi }^{0} ) $ ( V ? 0 ) , standard partial molar volumes of transfer $ (\Updelta_{\text{tr}} V_{\phi }^{0} ) $ ( Δ tr V ? 0 ) and hydration numbers have been determined for the amino acids. The $ \Updelta_{\text{tr}} V_{\phi }^{0} $ Δ tr V ? 0 values of l-serine are positive which suggest that hydrophilic–hydrophilic interactions between l-serine and DMF are predominant. The –CH₃ group of l-alanine has much more influence on the volumetric properties and the $ \Updelta_{\text{tr}} V_{\phi }^{0} $ Δ tr V ? 0 have smaller negative values. The results have been interpreted in terms of the cosphere overlap model.     

Standard Molar Volumes and Heat Capacities of Aqueous Solutions of Trifluoromethanesulfonic Acid at Temperatures up to 573 K and Pressures to 30 MPa

Densities and heat capacities of dilute aqueous solutions (0.025 to 0.4 mol⋅kg⁻¹) of trifluoromethanesulfonic acid (triflic acid) were measured with original high-temperature, high-pressure instruments at temperatures and pressures up to 574 K and 31 MPa, respectively. Standard molar volumes and standard molar heat capacities were obtained via extrapolation of the apparent molar properties to infinite dilution. The evolution of these standard derivative properties of triflic acid with temperature and pressure is qualitatively compared with that of other acids of different strengths.     

Partial Molar Volumes and Isentropic Compressions of Cyclic Ethers in Aqueous Solutions from 288.15 to 313.15 K at Atmospheric Pressure

The partial molar volumes and isentropic compressions of aqueous solutions of tetrahydrofuran, tetrahydropyran, 1,4-dioxane, tetrahydropyran-2-methanol, 3-hydroxytetrahydrofuran, and tetrahydrofurfuryl alcohol were measured at 288.15, 298.15, and 313.15 K. Results are analyzed in terms of the effects of group addition to the molar volumes and isentropic compressions. The temperature dependence of the molar volumes and compressions, and their group contributions, are used to characterize changes in hydration.     

Study of Aqueous Biomolecules with Magnetic Flux Using Density,Viscosity, and Surface Tension Probe at 304.15 K

Doses of 0.0150 weber m^?2 magnetic flux for 30 minutes are given to four series of biomolecules in aqueous medium, densities (ρ), viscosities (η), and surface tension (γ) were measured at 304.15 K. The vitamins and carbohydrates decrease densities and viscosities and the difference of density from magnet to aqueous solution in order of dextrose (? 0.00025 kg m^?3) > fructose (? 0.00021 kg m^?3) = B6 (? 0.00021 kg m^?3) > starch (? 0.00018 kg m^?3) > B1 (? 0.0018 kg m^?3), while viscosity in order of starch (? 0.0044 kg m^?1s^?1) > fructose (? 0.0037 kg m^?1s^?1) > B1(? 0.0018 kg m^?1s^?1) > dextrose (? 0.0016 kg m^?1s^?1) > B6 (? 0.0012 kg m^?1s^?1). The surface tension also decreases in vitamin and carbohydrate. The proteins show increase in ρ, η, and γ value hence casein decrease the density and viscosity. The glutamine show increase in density and surface tension while decrease in viscosity and vice versa to alanine. These orders of the data indicate the intermolecular force between water and bimolecules in magnetic flux.