Volumetric and Viscometric Studies on Some Inorganic Electrolytes in Water and in Water-SDS Solution Systems

The apparent molal volumes (φ _v ) of NaCl, NaNO₃, NH₄Cl, CuCl₂, CuSO₄, CoSO₄ and MgSO₄ in water and in water-SDS (Sodium dodecyl sulphate) solutions were determined from density measurements at 308.15, 313.15 and 323.15 K respectively. The limiting apparent molal volume at infinite dilution φ ^o _v which is practically equal to the partial molal volume V ^o ₂) of these electrolytes were found to be higher in water-SDS solution systems than those in water solutions. Viscosity coefficients (A and B) for these systems were also determined by Jones-Dole equation. All these electrolytes, except NH₄Cl exhibit structure making behaviour in water and in water-SDS solutions. Ammonium chloride showed structure breaking properties in water and in 0.01 molar water-SDS solutions. In 0.1 molar SDS solution, it showed structure making behaviour at the temperature range studied. The properties of these electrolytes in water and in water-SDS solution systems have been discussed in terms of the charge, size and hydrogen bonding effect.     

Molecular interactions in β-alanine-water-methanol solutions at 308.15 K on volumetric, viscometeric, and acoustic data

The density, viscosity and ultrasonic velocity for β-alanine solutions in aqueous and aqueous methanol medium at different concentrations has been determined at 308.15 K. The experimentally obtained data were used to evaluate the apparent molal volume and apparent molal adiabatic compressibility. The related thermodynamic parameters like partial molal volume as well as partial molal adiabatic compressibility at infinite dilution along with their corresponding constants S _v and S _k , respectively, give an insight to the nature of molecular interactions. The viscosity coefficient has also been calculated using Jones-Dole equation.     

Physicochemical investigation on interactions of some amino acids with aqueous tetra-butyl ammonium bromide solution at 298.15 K

Apparent molar volumes, viscosity B-coefficients, and apparent molar isentropic compressibilities of glycine, L-alanine, L-valine and L-leucine in 0.062, 0.125 and 0.256 mol kg^?1 aqueous tetra-butyl ammonium bromide (TBAB) solution have been determined at 298.15 K from their experimental density, flow time and sound speed measurements, respectively. The standard partial molar volumes and compressibilities are used to calculate the corresponding volume of transfer at infinite dilution, from water to aqueous TBAB solutions. The linear correlation of partial molar volumes for a homologous series of amino acids has been utilised to calculate the contribution of charged end groups and other alkyl chains of the amino acids to partial molar volumes. The hydration numbers of amino acids have also been determined. Viscosity B-coefficients have been calculated using the Jones–Dole equation. The values of the charged end groups contribution to the viscosity B-coefficients of the amino acids are calculated.     

Volumetric and compressibility studies for (L-arginine + D-maltose monohydrate + water) system in the temperature range of (298.15 to 308.15) K

The density and speed of sound of L-arginine (0.025–0.2 mol kg^?1) in aqueous + D-maltose (0–6 mass% of maltose in water) were obtained at temperatures of (298.15, 303.15 and 308.15) K. The apparent molar volume, limiting apparent molar volume, transfer volume, as well as apparent molar compressibility, limiting apparent molar compressibility, transfer compressibility, pair and triple interaction coefficients, partial molar expansibilities, coefficient of thermal expansion and also the hydration number, were calculated using the experimental density and speed of sound values. The results have been discussed in terms of solute–solute and solute–solvent interactions in these systems. Solute–solvent (hydrophilic–ionic group and hydrophilic–hydrophilic group) interactions were found to be dominating over solute–solute (hydrophobic–hydrophilic group) interactions in the solution, which increases with increase in maltose concentration.     

Isentropic partial molal compressibilities of alcohols in propylene carbonate at 25°C

The isentropic coefficients of compressibility of the homologous series of alcohols and diols R _n CH₂OH (n=2–6), CH₃CHOHR _n (n=1–5), 1,2-propanediol, 1,3- 1,4- and 2,3-butanediol, 1,5-pentanediol, and 1,7-heptanediol dissolved in propylene carbonate have been measured at 25°C. Isentropic partial molal compressibilities and group partial molal compressibilities at infinite dilution have been evaluated. The isentropic partial molal compressibilities of these alcohols and diols have been compared with the corresponding values in water. This comparison shows that the values in propylene carbonate are higher than in water by a factor of 10 due to an increased compressibility of the solvation sheath around nonpolar groups in PC.     

Volumetric and Ultrasonic Investigation of Glycylglycine in Aqueous FeCl<Subscript>3</Subscript> Solutions

Viscosity, ultrasonic velocity and density measurements have been carried out for glycylglycine in aqueous FeCl₃ solution as a function of molality at T=288.15 K, 298.15 K and 308.15 K. The experimental data have been used to derive properties such as isentropic compressibility (κ _S ), change in isentropic compressibility (Δκ _S ), relative change in isentropic compressibility (Δκ _S /κ ₀), apparent molar compressibility, volume and their limiting apparent molar quantities along with the constants S _K , S _V and viscosity B-coefficient. The obtained thermodynamic properties have been discussed in terms of molecular interactions.     

Partial Molar Volumes of Some of α-Amino Acids in Binary Aqueous Solutions of MgSO4·7H2O at 298.15 K

The apparent molar volume, V ^o _{φ, 2}, of glycine, alanine, α-amino-n-butyric acid, valine and leucine have been determined in aqueous solutions of 0.25, 0.5 and 1.0 mol⋅dm⁻³ magnesium sulfate, and the partial specific volume from density measurements at 298.15 K. These data have been used to calculate the infinite dilution apparent molar volume, V ^o _2,m , group contribution of amino acids and partial molar volume of transfer, Δ_tr V _2,m ^o, from water to aqueous magnesium sulfate solutions. The linear correlation of V _2,m ^o for a homologous series of amino acids has been utilized to calculate the contributions of charged end groups (NH₃ ⁺, COO⁻), CH₂ - groups and other alkyl chains of amino acids to V _2,m ^o. The results for Δ_tr V _2,m ^o of amino acids from water to aqueous magnesium sulfate solutions have been interpreted in terms of ion-ion, ion-polar, hydrophilic-hydrophilic and hydrophobic-hydrophobic group interactions. The values of the standard partial molar volume of transfer for the amino acids with different hydrophobic contents, from water to aqueous MgSO₄ are in general positive, indicating the predominance of the interactions of zwitterionic/hydrophilic groups of amino acids with ions of the salt. The hydration number decreases with increasing concentration of salt. The number of water molecules hydrated to amino acids decreases, further strengthening the predominance of ionic/hydrophilic interactions in this system.     

Solution thermodynamics of first-row transition elements. 4. Apparent molal volumes of aqueous ZnSO4 and CuSO4 solutions from 15 to 55°C

The apparent molal volumes of ZnSO ₄ and CuSO ₄ have been determined from density data over the temperature range 15–55°C and concentration range 0–15 molal. The volume data have been fitted to the Pitzer formalism over the entire temperature and concentration range. The volume changes for the formation of ZnSO ₄ and CuSO ₄ ion pairs have been estimated over the temperature range covered and the partial molal volumes of ZnSO ₄ and CuSO ₄ ion pairs have been derived. The results were used to explain the hydration structure of the ion pair. UV spectral effects accompanying a change of temperature in the 15–65°C range in CuSO ₄ solution indicate direct coordination of sulfate anion to the cupric cation. The process is favored by an increase in temperature.     

Ion association and departure from additivity of equivalent conductance as a function of pressure

The equivalent conductance of mixtures of 0.01 equivalent/liter solutions of MgCl₂ and Na₂SO₄ were measured as a function of pressure at 25°C. Departures from additivity are used to infer the pressure dependence of the concentration of MgSO₄ ion pairs. The results are consistent with the pressure dependence of the molal dissociation constant of MgSO₄ obtained from pressure conductance studies on aqueous solutions of MgSO₄.     

Acoustic and volumetric studies of uracil in aqueous urea solution at different temperatures

Volumetric, viscometric and ultrasonic studies of uracil in an aqueous urea solution in varying concentration of 2, 3 and 5?M have been carried out at 298, 308 and 318?K. The uracil concentration in the aqueous urea solution varies from 0.05% to 0.4%. Density (ρ), viscosity (η) and sound speed (u) have been measured. The experimental data are used for computing various thermodynamic and acoustic parameters, namely apparent molar volume, isentropic compressibility, apparent isentropic compressibility, relative association, intermolecular free length, acoustic impedance, viscous relaxation time, hydration number, Gibb's free energy, classical absorption coefficient of the solution and viscosity data have been further analysed in the light of Masson's equation and Jones–Dole's equations, respectively. The results have been discussed in terms of solute–solute and solute–solvent interaction and the structural changes of the solutes in solutions. The effect of variation of temperature on these interactions has also been investigated.     

Ultrasonic Study of Basic α‐Amino Acids in Different Acetate Salt Solutions at Different Temperatures

The ultrasonic velocity (U), has been measured for three α‐amino acids, namely L‐lysine monohydrochloride, L‐arginine and L‐histidine in solutions (1 mol/L aqueous) of sodium acetate (SA), potassium acetate (PA) and calcium acetate (CA) at different temperatures (303.15, 308.15, 313.15, 318.15 and 323.15 K). With the help of these results various ultrasonic derived parameters, viz. isentropic compressibility (κ_s), change in isentropic compressibility (Δκ_s), relative change in isentropic compressibility (Δκ_r), specific acoustic impedance (Z), relative association (RA), and apparent molal compressibility (?) have been estimated. The results have been interpreted in the light of intermolecular interactions between solute and solvent.     

Densities and compressibilities of aqueous sodium carbonate and bicarbonate from 0 to 45°C

The densities and the sound speeds of aqueous NaHCO₃ and Na₂CO₃ solutions were measured from 0.05 to 1.0m and from 0 to 45°C. These data were fitted to functions of molality and temperature and were used to calculate the apparent molal volumes V_? and compressibilites κ_φ of these solutions. Polynomial expression for V_? and κ_φ as functions of molality and temperature have been determined. The partial molal volumes and compressibilities of these solutions and literature data have been used to determine the volume ΔV and compressibility Δκ changes for the ionization of carbonic acid in aqueous solutions. These values of ΔV and Δκ have been used to estimate the effect of pressure on the ionization constants for carbonic acid from 0 to 45°C. The calculated pressure coefficients are in good agreement with the measured values.     

The effect of pressure on the ionization of water at various temperatures from molal-volume data1

The apparent molal volumes of dilute (0.002 to 1.0m) aqueous HCl and NaOH solutions have been determined at 0, 25, and 50°C and NaCl solutions at 50°C. The partial molal volumes ( ) of HCl, NaOH, and NaCl solutions have been determined from these apparent molal volumes and other reliable data from the literature. The partial-molal-volume changes ( ) for the ionization of water, H₂OH⁺+OH^–, have been determined from 0 to 50°C and 0 to 1m ionic strength from the partial molal volumes of HCl, NaOH, NaCl, and H₂O. The partial molal compressibilities ( for HCl, NaOH, NaCl, and H₂O have been estimated from data in the literature and used to determine the partial molal compressibility changes ( ) for the ionization of water from 0 to 50°C and 0 to 1m ionic strength. The effect of pressure on the ionization constant of water has been estimated from partial-molal-volume and compressibility changes using the relation from 0 to 50°C and 0 to 2000 bars. The results agree very well with the directly measured values.Contribution Number 1548 from the University of Miami.     

Insight into molecular interactions and solvation properties of methylammonium perchlorate in acetonitrile-dimethylsulfoxide binary mixtures: Compressibility,viscometric and dissolution thermodynamic studies

Densities (ρ), ultrasonic velocities (u) and viscosities (ƞ) of Methylammonium perchlorate (CH₃NH₃ClO₄) in binary solvent mixtures of Acetonitrile (AN) and Dimethylsulfoxide (DMSO) containing 0.0, 0.20, 0.40, 0.60, 0.80 and 1.0 ​mol fraction of DMSO at various temperatures ranging from 298K–328K at atmospheric pressure, have been measured. From the experimental data important parameters, namely, apparent molal volume (V_Φ), isentropic compressibility (K_s), limiting apparent molal isentropic compressibility (K^o_s,ɸ), A and B-viscosity coefficients from Jones-Dole equation, B/V_ɸ^o values and viscous flow related thermodynamic properties have been derived. Interpretation of the obtained thermodynamic parameters was done with regards to solute-solvent and solute-solute interactions and structure breaking and making potential of the solutes in solution. To evaluate the extent of preferential solvation, K^o_s,ɸ values and B-coefficients for the electrolytes have been further split up into the contribution of individual ion (K^o_s,ɸ± and B_± values) by reference electrolyte method.     

Seawater—A test of multicomponent electrolyte solution theories. II. Enthalpy of mixing and dilution of the major sea salts

In a continuing effort to predict the physicochemical properties of seawater from the properties of single aqueous electrolyte solutions, the pairwise heats of mixing at constant molal ionic strength,I=1.0 ional, have been determined for the six possible pairs of salts from the set (NaCl, Na₂SO₄, MgCl₂, MgSO₄) at 30°C. In addition, heats of dilution for two aqueous solutions formed from these salts and havingI=1.0 ional have been determined at 30°C. In order to present the most thermodynamically consistent results, it was found necessary to apply a correction term to the relative apparent equivalent enthalpies given in the literature at 30°C. These correction terms derived from a consideration of published results on heats of dilution at very low concentrations. Further, in order to make predictions for seawater at 25°C, it was deemed desirable to refit existing heat-capacity data. The heats relative apparent equivalent enthalpies for the two mixtures mentioned as well as for seawater. The estimates are based on the theoretical equation of Reilly and Wood for charge-asymmetric mixtures which derives from the work of Friedman. In the most applicable cases, the estimates agree with experimental relative apparent equivalent enthalpies to within 5%. In general, the results substantiate the theoretical equation.Taken in part from the Ph.D. dissertation of W. H. Leung, University of Miami, Miami, Florida 33149.     

Volume and compressibility changes on mixing aqueous solutions of the amino acid and poly(ethylene glycol)

The volume and compressibility changes on mixing aqueous solutions of the amino acid and poly(ethylene glycol) were measured with a vibration densimeter and a sing-around velocimeter at 298.15 K. For the system of alanine-PEG-H₂O, the additivity rule for the mean apparent molal volume and compressibility at infinite dilution held, and the excess volume and compressibility changes on mixing were obtained. For the system of glycine-PEG-H₂O, the additivity rule for the mean apparent molal compressibility at infinite dilution did not hold. While the mean apparent molal volume and compressibility changes were negative and positive for the systems of another amino acid-PEG-H₂O, respectively, where amino acids were valine, isoleucine, leucine, phenylalanine, and tryptophan. These results suggest that glycine and alanine are excluded from the hydration layer around PEG chain and the amino acids with a larger side chain than alanine are bound to the PEG chain due to the hydrophobic interaction. The hydration number per monomer around PEG chain was estimated to be 3.9.     

Thermodynamic properties of solutions of sodium di-hydrogen phosphate in (1-propanol + water) mixed-solvent media over the temperature range of (283.15 to 303.15) K

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.     

Physico-chemical studies of a biologically active molecule (L-valine) predominant in aqueous alkali halide solutions with the manifestation of solvation consequences

The apparent molar volume (?_V), viscosity B-coefficient and molar refraction (R_M) have been determined of L-valine in aqueous solution of LiCl, NaCl and KCl at 298 K, 303 K and 308 K from density (ρ), viscosity (η) and refractive index (n_D) measurements, respectively. The limiting apparent molar volumes (?_V⁰) and experimental slopes (S_V*) derived from the Masson equation have been interpreted in terms of solute–solvent and solute–solute interactions, respectively. The viscosity data were analysed using the Jones–Dole equation and the derived parameter B has also been interpreted in terms of solute–solvent interactions in the solutions. Molar refraction (R_M) has been calculated using the Lorentz–Lorenz equation.     

Structural interaction leading to volumetric changes in aqueous solutions of nitrates of rubidium,cesium, strontium,yttrium, and gallium at different temperatures

Densities of the aqueous dilute solutions of rubidium, cesium, strontium, yttrium, and gallium nitrate were measured at different temperatures ranging from (293.15–343.15) K and atmospheric pressure. From these density values, the apparent molal volumes were calculated and fitted to Masson’s correlation and the temperature dependence was correlated by a second order polynomial. The apparent molal volumes at infinite dilution and experimental slopes have been interpreted in terms of ion–solvent and ion–ion interactions, respectively. The measurements include density as per ASTM D-4052, refractive index (nD²⁵) at sodium D line at 25 °C. Thermal isobaric expansibility was calculated and structure making and structure breaking behaviour of electrolytes were inferred from the sign of the second derivative of apparent molal volumes with respect to temperature at constant pressure. The experimental apparent molal volume was compared with the available literature value.     

Divalent sulfate ion pairs in aqueous solutions at pressures up to 2000 atm

Electrical conductance measurements have been made at various temperatures and at concentrations from ca. 0.00005 to ca. 0.01M in aqueous solutions of MgSO₄, CaSO₄, CoSO₄ and NiSO₄ at pressures up to 2000 atm. The data have been analyzed with the Fernandez-Prini modification of the Fuoss-Hsia conductance equation to obtain the molal dissociation constants K _m at each pressure. The results for V^°, obtained from the pressure dependence ofK _m,are compared with other experimental data and with values calculated from acoustically derived multistate dissociation models.