Concentration dependence of NaCl in a wide range of temperatures and pressures

We use our own and literature data on density, ultrasound propagation velocity, and isobaric heat capacity to study the concentration, temperature, and pressure dependences of solvation numbers in aqueous NaCl solutions. We show that, in the parameter range: m = 0–6.0 mol·kg^?1, p = 1–1000 bar, and T = 283.15–323.15 K, the solvation numbers decrease with increasing concentration, pressure, and temperature.     

Thermodynamics of aqueous NH4Br solutions over wide ranges of concentrations and temperatures

The enthalpies of solution and dilution of aqueous solutions of NH₄Br at electrolyte concentrations lower than 6 mol/kg solvent are measured at 277 and 288 K. The generalized equation for the enthalpy as a function of concentration and temperature is derived using the data for 298 and 313 K. The thermodynamic properties of NH₄Br solutions at concentrations up to saturated solutions and at temperatures of 273, 298, 323, and 348 K are discussed.     

Adsorption dynamics over a wide range of breakthrough concentrations

Conclusions A simple method is proposed for carrying out analytical calculations on adsorption dynamics; by its use one can make allowance for longitudinal effects in determining coefficients of external mass transfer and internal diffusion, and dynamic bed activities.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 56–62, January, 1981.     

Standard thermodynamic properties of H3PO4(aq) over a wide range of temperatures and pressures

The densities and heat capacities of solutions of phosphoric acid, 0.05 to 1 mol kg-1, were measured using flow vibrating tube densitometry and differential Picker-type calorimetry at temperatures up to 623 K and at pressures up to 28 MPa. The standard molar volumes and heat capacities of molecular H3PO4(aq) were obtained, via the apparent molar properties corrected for partial dissociation, by extrapolation to infinite dilution. The data on standard derivative properties were correlated simultaneously with the dissociation constants of phosphoric acid from the literature using the theoretically founded SOCW model. This made it possible to describe the standard thermodynamic properties, particularly the standard chemical potential, of both molecular and ionized phosphoric acid at temperatures up to at least 623 K and at pressures up to 200 MPa. This representation allows one to easily calculate the first-degree dissociation constant of H3PO4(aq). The performance of the SOCW model was compared with the other approaches for calculating the high-temperature dissociation constant of the phosphoric acid. Using the standard derivative properties, sensitively reflecting the interactions between the solute and the solvent, the high-temperature behavior of H3PO4(aq) is compared with that of other weak acids.     

Disperse aqueous systems based on (S)-lysine in a wide range of concentrations and physiologically important temperatures

Russian Chemical Bulletin - It was shown for the first time using a complex of physicochemical methods (dynamic and electrophoretic light scattering, nanoparticle tracking analysis, transmission...     

New intermolecular interaction potential for simulation of water and aqueous solutions in a wide range of state parameters

A new semiempirical method for derivation of additive effective potentials is proposed. Local features of the shape of the potential energy surface of water dimers are approximated by Gaussian functions. Optimum geometric parameters of nonlinear bifurcated and inverted dimers, obtained from quantum-chemical calculations are constants of the new BMW potential. Free parameters of the potential were chosen based on the results of Monte Carlo simulation of the structural and thermodynamic functions of water in a wide range of state parameters (268 K T 673 K, 0.1 MPa p 400 MPa). Calculations revealed rather high concentrations of the bifurcated and inverted dimers in the systems of H-bonds of water models. Clustering of non-tetrahedral fragments of the network of H-bonds is responsible for a microheterogeneous structure of water on the microscopic level.     

Conductance of aqueous NaCl solutions at pressures up to 2000 atm

Electrical conductance measurements are reported for aqueous NaCl solutions at 25°C as a function of concentration up to 0.02M and pressures up to 2000 atm. The data were analyzed with the Fuoss-Hsia-Fernandez-Prini (FHFP) equation. The standard error of fit, , varies from 0.04 at 1 atm to 0.10 at 2000 atm. The increase of with pressure arises from increasing non-randomness in the distribution of errors about the FHFP equation suggesting that modifications in the theory are necessary. The pressure dependence of _O for NaCl and KCl is nearly identical.Contribution of the Scripps Institution of Oceanography, New Series     

Viscosity of aqueous calcium chloride solutions at high temperatures and high pressures

Viscosity of six (0.10, 0.33, 0.65, 0.97, 1.40, and 2.00) mol kg⁻¹ binary aqueous CaCl₂ solutions has been measured with a capillary-flow technique. Measurements were made at pressures up to 60 MPa. The range of temperature was from 293 to 575 K. The total uncertainty of viscosity, pressure, temperature, and composition measurements was estimated to be less than 1.6%, 0.05%, 15 mK, and 0.014%, respectively. The effect of temperature, pressure, and concentration on viscosity of binary aqueous CaCl₂ solutions was studied. The measured values of viscosity of CaCl₂(aq) were compared with data, predictions, and correlations reported in the literature. The temperature and pressure coefficients of viscosity of CaCl₂(aq) were studied as a function of concentration and temperature. The viscosity data have been interpreted in terms of the extended Jones–Dole equation for the relative viscosity (η/η₀) to accurate calculate the values of viscosity A- and B-coefficients as a function of temperature. The derived values of the viscosity B-coefficients were compared with the values calculated from the ionic B-coefficient data. The physical meaning parameters V and E in the absolute rate theory of viscosity and hydrodynamic molar volume (effective rigid molar volume of salt) V_k were calculated using present experimental viscosity data. TTG model has been used to compare predicted values of the viscosity of CaCl₂(aq) solutions with experimental values at high pressures.     

Phase behaviors of poly(sulfobetaine methacrylate) in various concentrations of NaCl aqueous solutions at critical transparent state

The phase behaviors of poly(sulfobetaine methacrylate) (polySBMA) in various concentrations of NaCl aqueous solutions at critical transparent state were investigated utilizing UV–vis analytical techniques. The effects of the molecular weight and temperature on the phase behavior of polySBMA at the critical transparent state were discussed in detail depending on the relationship between the concentration of NaCl, the concentration of critical polySBMA structural unit, and the molar ratio (R_C) of NaCl to the critical polySBMA structural unit. The results demonstrate that there exists a positive polymer concentration effect on the transparency. A relationship between the molecular weight, the concentration of NaCl, and the concentration of critical polySBMA structural unit was obtained, which provides a new method for measurement of the molecular weight of polySBMA. The polymer concentration effect for the polySBMA solutions at lower temperature was remarkable, which was similar to that for the polySBMA solutions with higher molecular weight.     

The vapour pressures over saturated aqueous solutions of sodium and potassium acetates,chlorates, and perchlorates

Vapour pressures of water over saturated solutions of sodium acetate, potassium acetate, sodium perchlorate, and potassium perchlorate were determined over the (278 to 318) K temperature range and compared with available in the literature data. The cases of saturated solutions of sodium chlorate and potassium chlorate are also considered. The determined vapour pressures were used to obtain the water activities, the osmotic coefficients, and the molar enthalpies of vaporization in considered systems.     

Structure and dynamics of rodlike polyester with long n-alkyl side chains over a wide range of temperatures by solid state C NMR

Solid state ¹³C NMR experiments on poly(p-biphenylene terephthalate) with long n-dodecyl side chains have been carried out over a wide range of temperatures, in order to elucidate conformational and dynamical behavior of the polyester in the crystalline state and thermotropic liquid crystalline state. From these experimental results, it is found that at temperatures from room temperature to 80 °C the n-alkyl side chains take both of the immobile and the mobile regions, and at temperatures above 120 °C take only the mobile region. In the immobile region the n-alkyl side chains are in the all-trans zigzag conformation and in the mobile state are undergoing fast exchange between the trans and gauche conformations. On the other hand, the terephthalate moiety of the main chain undergoes rotational motion after the melt of n-alkyl side chains as the temperature is increased.     

The atmospheric oxidation of ethyl formate and ethyl acetate over a range of temperatures and oxygen partial pressures

The Cl‐atom‐initiated oxidation of two esters, ethyl formate [HC(O)OCH₂CH₃] and ethyl acetate [CH₃C(O)OCH₂CH₃], has been studied at pressures close to 1 atm as a function of temperature (249–325 K) and O₂ partial pressure (50–700 Torr), using an environmental chamber technique. In both cases, Cl‐atom attack at the CH₂ group is most important, leading in part to the formation of radicals of the type RC(O)OCH(O^?)CH₃ [R = H, CH₃]. The atmospheric fate of these radicals involves competition between reaction with O₂ to produce an anhydride compound, RC(O)OC(O)CH₃, and the so‐called α‐ester rearrangement that produces an organic acid, RC(O)OH, and an acetyl radical, CH₃C(O). For both species studied, the α‐ester rearrangement is found to dominate in air at 1 atm and 298 K. Barriers to the rearrangement of 7.7 ± 1.5 and 8.4 ± 1.5 kcal/mole are estimated for CH₃C(O)OCH(O^?)CH₃ and HC(O)OCH(O^?)CH₃, respectively, leading to increased occurrence of the O₂ reaction at reduced temperature. The data are combined with those obtained from similar studies of other simple esters to provide a correlation between the rate of occurrence of the α‐ester rearrangement and the structure of the reacting radical. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 397–413, 2010     

Prediction of hydrogen solubility in heavy hydrocarbons over a range of temperatures and pressures using molecular dynamics simulations

Using the method of molecular dynamics (MD), we have estimated the solubility of hydrogen in heavy hydrocarbons for a range of temperatures and pressures. Heavy hydrocarbon systems are known to be challenging not only for experimental measurements but also for reliable estimations using traditional equations of state (EOS). The simulation system used was designed with semi-permeable membranes to mimic actual experimental studies of gas solubility. Binary interaction parameters between the solute gas and the solvent (heavy hydrocarbons) components were adjusted when necessary to improve agreement with experimental results and then used in subsequent multi-component studies. Temperature and pressure ranges studied included higher temperatures and pressures which are especially difficult to investigate experimentally. Simulation results were finally used to adjust the binary interaction parameters (BIP) in simulation packages (e.g. Aspen) to enable quick and reliable predictions.     

Solvation of a hydrogen isotope in aqueous methanol, NaCl, and KCl solutions

The muon hyperfine coupling constant (hfc) of the light hydrogen isotope muonium (Mu) was measured in aqueous methanol, NaCl, and KCl solutions with varying concentrations, in deuterated water, and in deuterated methanol. The muon hfc is shown to be sensitive to the size and composition of the primary solvation shell, and the three-dimensional harmonic oscillator model of Roduner et al. (J. Chem. Phys. 1995, 102, 5989) has been modified to account for dependence of the muon hfc on the methanol or salt concentration. The muon hfc of Mu in the aqueous methanol solutions decreases with increasing methanol concentration up to a mole fraction (chiMeOH) of approximately 0.4, above which the muon hfc is approximately constant. The concentration dependence of the muon hfc is due to hydrophobic nature of Mu. It is preferentially solvated by the methyl group of methanol, and the proportion of methanol molecules in the primary solvation shell is greater than that in the bulk solution. Above chiMeOH approximately 0.4, Mu is completely surrounded by methanol. The muon hfc decreases with increasing methanol concentration because more unpaired electron spin density is transferred from Mu to methanol than to water. The unpaired electron spin density is transferred from Mu to the solvent by collisions that stretch one of the solvents bonds. The amount of spin density transferred is likely inversely related to the activation barrier for abstraction from the solvent, which accounts for the larger muon hfc in the deuterated solvents. The muon hfc of Mu in electrolyte solution decreases with increasing concentration of NaCl or KCl. We suggest that the decrease of the muon hfc is due to the amount of spin density transferred from Mu to its surroundings being dependent on the average orientation of the water molecules in the primary solvation shell, which is influenced by both Mu and the ions in solution, and spin density transfer to the ions themselves.     

Bacterial attachment over a wide range of ionic strengths

The number of bacterial cells adhered on a glass surface was counted over a wide range of ionic strengths. The counted number increased linearly with the square root of time. The rate of attachment increased with the increase in ionic strength and then plateaued. The rate of attachment was analyzed on the basis of the potential barrier between the surface of the bacterial cell and that of the substratum. An equation for formulating the dependence of the attachment rate on the ionic strength was proposed, which seems to be useful for the systematic understanding of bacterial attachment in various environments, from terrestrial to marine.     

Thermal properties and interactions of l-proline in aqueous solutions of NaCl or KCl at different temperatures

The enthalpies of solution of l-proline in aqueous electrolyte solutions within the electrolyte molality range up to 4.9 mol kg^?1 of NaCl and up to 4.0 mol kg^?1 of KCl at 288, 298 and 313 K have been measured by the calorimetric method. Enthalpies of transfer of l-proline from water to aqueous electrolyte solutions up to saturation have been derived at 273–348 K. The enthalpic and heat capacity parameters of pair and triplet interaction of l-proline with electrolyte in water have been evaluated. Enthalpic parameters of pair interaction at 298 K have been compared to similar parameters for glycine and l-alanine. The temperature changes of reduced enthalpy, and also the change of entropy and reduced Gibbs energy of transfer of l-proline from water to aqueous electrolyte solution at temperature rise from 273 to 323 K have been determined. It has been shown that the entropy–enthalpy compensation takes place for transfer processes.