Electro-osmotic pumping of sodium chloride solutions

Electro-osmotic pumping (EOP) theory and its characteristics (transport numbers, brine concentration, current density, current efficiency, electro-osmotic coefficients, etc.) of Selemion AMV and CMV ion-exchange membranes were studied. The brine concentration increased with increase in current density and feed water concentration. Current efficiency was nearly constant in a wide range of current densities and feed water concentrations. The water flow through the membranes also increased with increasing current density and feed water concentration. The increase in water flow increased the current efficiency significantly. Consequently, water flow through electrodialysis (ED) membranes had a positive effect on ED. Electro-osmotic coefficients decreased with increasing feed water concentration. Osmotic flow in EOP-ED decreased relative to the total flow with increasing current density while the electro-osmotic flow increased relative to the osmotic flow. Osmotic flow significantly contributes to the total water flow in EOP. Selemion AMV and CMV membranes performed well for salt concentration. A simple membrane potential measurement has been demonstrated to function reasonably satisfactorily to predict membrane performance for salt concentration.     

Aggregation of sodium dodecyl sulfate in aqueous sodium chloride solutions

Summary Aqueous solutions of sodium dodecyl sulfate with added sodium chloride (0–0.3 mol kg^–1) were studied at 298.2 K in order to calculate the molar standard free energy of micelle formationG _m . The following properties were measured: (i) aggregation number by membrane osmometry, (ii) counter-ion binding and sodium ion activities by electromotive force, (iii) critical micelle concentration by electromotive force and fluorescence spectrophotometry. The results indicate thatG _m . is independent of the NaCl concentration.     

Electrical conductance of concentrated aqueous magnesium chloride at 25°C

Precise conductivity results are reported for concentrated aqueous solutions of magnesium chloride at 25°C. At concentrations above 0.5 mol-dm^–3(M) the results are 0.1–0.15 conductance units lower than the values recommended in a recent critical review of literature data.     

Electrical conductance of solutions of lithium nitrate in 1,3-diaminopropane

Electrical conductances and densities of the LiNO₃-1,3-diaminopropane system have been measured as a function of composition and temperature. The results suggest that the solvent molecules may act as bridges between Li⁺ ions at higher concentration of LiNO₃.     

Electrical conductance of aqueous solutions of KCl solutions at pressures up to 2000 atm

Electrical conductance measurements are reported for aqueous KCl solutions at 25°C as a function of concentration up to 0.02 M and pressure up to 2000 atm. The data from 103 runs were analyzed with the Fuoss-Hsia-Fernandez-Prini (FHFP) equation. The standard error of fit varies from 0.018 at 1 atm to 0.12 at 2000 atm. The increase of with pressure arises from increasing nonrandomness in the distribution of errors about the FHFP equation, suggesting that modifications in the theory are necessary. Departures from the Walden product for KCl as a function of pressure are compared with MgSO₄ and CaSO₄ in aqueous solutions.     

Thermodynamics of sodium chloride solutions at high temperatures

Osmotic coefficients are reported from vapor-pressure-lowering measurements on sodium chloride solutions at concentrations from approximately 4m to saturation and at temperatures from 75° C to 300° C. In combination with previously reported measurements at lower concentrations, these results allow a correlation of free energies for the system NaCl–H₂O over a range of concentrations and temperatures that is unprecedented for any aqueous electrolyte. Activity coefficients and other thermodynamic quantities for both salt and water have been calculated for the complete range of concentrations and temperatures. Calculated heats of solution and standard partial molal entropies agree well with calorimetric determinations where comparison is possible. The excess partial molal entropy of the salt is informative concerning structural effects and their changes with temperature and concentration.Presented in part at the 160th National Meeting of the American Chemical Society, Chicago, Illinois, September 1970.     

Amino acid hydration in aqueous ammoniu chloride and sodium chloride solutions

Partial volumes $\bar V^0$ of amino acids in aqueous NH₄Cl and NaCl solutions are discussed. The salts have different effects on water structure. The contributions of the charged NH ₃ ⁺ and COO^? groups of amino acids are found. Structural characteristics of hydrated complexes are calculated: partial volumes of water inside and outside the hydration sphere and hydration numbers. The same value of $\bar V^0$ (NH ₃ ⁺ , COO^?) is achieved at a higher NH₄Cl concentration. The two salt systems with the same $\bar V^0$ (NH ₃ ⁺ , COO^?) have similar values of the partial volumes of water and hydration numbers.     

The heat of dehydration of concentrated sodium chloride and potassium chloride solutions

The molar heats of dehydration, ΔH¯_dehyd., of concentrated sodium chloride and potassium chloride solutions were measured with a differential scanning calorimeter in the scanning and isothermal modes. The overall ΔH¯_dehyd. was found to be 44.5 and 44.3 kJ mole^?1 H₂O for NaCl and KCl solutions respectively. There is an astonishing difference between concentrated NaCl and KCl solutions in the way water is lost. The number of fractions of heat dehydration were 2 for NaCl and 3 for KCl. The excess ΔH¯_dehyd. was about 10 kJ mole^?1 H₂O for fraction II of NaCl, and 17 and 55 kJ mole^?1 H₂O for fractions II and III, respectively, of KCl.     

Optimization of plasma treatment of aqueous sodium chloride solutions

The effect of pressure in a plasma reactor on the synthesis of mixtures of H₂O₂ and ClO ₂ ^- has been studied. The yield of oxidants, selectivity for chlorites, the rate of the process, and its energy consumption have been treated as optimization parameters. Functional dependences of the optimal time of the plasma treatment of NaCl solutions on the reactor pressure with respect to parameters, such as the process selectivity and chlorite yield, have been determined.     

Ionization of methyl orange in aqueous sodium chloride solutions

Ionization constants of sodium 4′-dimethylaminoazobenzene-4-sulphonate (methyl orange) were determined by means of spectrophotometric measurements in water and in aqueous sodium chloride solutions with molalities up to 2 mol·kg⁻¹ at temperatures between 278.15 K and 333.15 K. The temperature dependence of the thermodynamic acidity constant shows a slight curvature in accordance with published data. The influence of sodium chloride on the methyl orange deprotonation was assessed by the measurement of stoichiometric acidity constants in this ionic medium. The Pitzer theory, widely used in the evaluation of the excess free energy of non-ideal electrolyte solutions, was applied to the computation of the activity coefficients of the chemical species involved in the equilibria and a good fit of those equations to the experimental data was observed, at all temperatures under consideration.     

Electrical conductance of CHCl3 solutions of polyethylene oxide doped with KCI

CHCl3 solutions containing a few percent polyethylene oxide PEO (M_W = 200 000) or the low-molecular model dioxane are stirred at 50°C during more than 100 h in the presence of small amounts of KCl. The specific conductance, the viscosity and the density of the solutions are measured at 25°C as a function of time. Both PEO and dioxane act as ligands improving the solubility of KCl. The relaxation times are of the order of several hours. After 40 h or more the viscosity of the solutions increases in a spectacular way. However, the most striking observation is that the specific conductance of the polymeric solutions at 25°C is systematically 5% higher than the value measured with the same sample at 45°C, just as for metals. The effect of the dilution of the primary stirred solutions either in the pure solvent or in the initial polymer solution is investigated. These results are discussed in terms of a three-step mechanism in the polymer systems: (1) Loading of the coils to polymeric cations with a full elementary charge, as a consequence of charge transfer interactions of the crown-ether type with numerous K⁺ ions penetrating into the coils; (2) Electron tunnelling conduction of the Hamill—Ceulemans type from one positive coil to the neighbouring one; (3) Alteration of the structure of the coils and of their hydrodynamic radius by the motions of K⁺ in the coils. These ‘brachiation’ motions by a hopping mechanism result from an increased mobility of the complexed K⁺ ions, which is also the origin of the Zundel effect. They do not directly contribute to the conductance but are responsible for the delayed increase of the viscosity.     

Transference numbers of sodium chloride in concentrated aqueous solutions and chloride conductances in several concentrated electrolyte solutions

Stable chlorine electrodes with low bias potentials have been developed by introducing 25% Ir+75% Pt electrodes and an improved gas line. With their use in cells with transference, cation constituent transference numbers have been measured at 25°C in NaCl solutions from 1.7 to 6 modal. These results agree well with four other sets of data in the literature but disagree with two further sets based on emf determinations with Ag/AgCl electrodes. A table of best NaCl transference numbers is proposed. The conductances of the chloride ion-constituent in concentrated NaCl, KCl, and HCl solutions are compared.     

Electrical conductivity of lithium chloride solutions in the propanol-water system

Electrical conduction of lithium chloride solutions in the propanol-water system was studied in the temperature range by using the conductometric method. The electrical conductivity of the solutions was determined in relation to the contents of water and lithium chloride.     

Adiabatic and isothermal compressibility of aqueous solutions of sodium chloride

By the example of aqueous solutions of sodium chloride an approach is developed to obtain the hydration number, molar volume and compressibility of hydrate complexes using the data on adiabatic and isothermal compressibility. It is shown that the results of calculations based on isothermal and adiabatic compressibility are consistent with each other     

Dilute solution properties of poly(dimethyldiallylammonium chloride) in aqueous sodium chloride solutions

MW fractions of poly(dimethyldiallylammonium chloride) (PDMDAAC) were prepared by preparative size-exclusion chromatography and characterized by static and dynamic light scattering, viscometry, size-exclusion chromatography, and electrophoretic light scattering, in 0.50M NaCl solution. The behavior of fractions with MW < 2 × 10⁵ was as expected for a strong polyelectrolyte in a good solvent, with a Mark-Houwink exponent of ca. 0.8, and MW-dependencies of the hydrodynamic radius and the radius of gyration of corresponding magnitude. At higher MW, curvature appears in the MW-dependencies, which can be best explained by the presence of branching. While this notably lowers the intrinsic viscosity at high MW, the electrophoretic mobility is unchanged regardless of molar mass. Thus, the branched polymers display the electrophoretic free-draining behavior characteristic of linear polyelectrolytes. ©1995 John Wiley & Sons, Inc.     

Electrical conductivity of aqueous sodium hydroxide solutions at high temperatures

Electrical conductivities of dilute sodium hydroxide aqueous solutions have been determined at 75, 100 and 150°C at 1.6 MPa using a recently developed DC-measuring technique especially suited for the study of aqueous solutions above room temperature. The data were analyzed with modern theories to obtain the infinite dilution conductivity and the association constant at the three temperatures.     

Electrical conductivity of lithium chloride solutions in the system isopropyl alcohol-water

Electrical conductivity of lithium chloride solutions in the system isopropyl alcohol-water in the temperature range 290–323 K was studied. The dependences of the specific and molar electrical conductivity of the solutions on the concentration of water and lithium chloride were determined.     

Mechanism and kinetics of the reaction of ozone with sodium chloride in aqueous solutions

It is shown experimentally that Cl⁻ appreciably accelerates ozone decomposition in water (τ_1/2 = 1.5 h versus 6 h in pure water). The decomposition of ozone in NaCl solutions includes the reversible reaction of ozone with the chloride ion (O₃ + Cl⁻ → O₃⁻ + Cl) as the key step, which is followed by the development of a chain reaction in which chain propagation is performed alternately by the chlorine atom Cl and its monoxide ClO. The current concentrations of the chlorine atom are rather low ([Cl] ∼ 10⁻¹⁴ mol/l). The overall process is satisfactorily described by a first-order rate law with respect to ozone. The decomposition of ozone in aqueous solutions of NaCl is not accompanied by the formation of products other than oxygen. In particular, no noticeable amounts of hypochlorites and chlorates are observed. This is particularly significant for medicinal applications of ozonized isotonic solutions.