Thermodynamic properties of chloro-complexes of silver chloride in aqueous solution

Available data on the solubility of silver chloride in aqueous solutions of HCl, NaCl, KCl, LiCl, and NH₄Cl, along with potentiometric measurements of the activity of Ag⁺ in aqueous NaCl–NaClO₄ mixtures, have been analyzed to obtain the thermodynamic properties of the (AgCl)⁰, AgCl ₂ ^– , AgCl ₃ ^2– , and AgCl ₄ ^3– complexes. Results obtained include the stability constants of the complexes and 25°C, the virial parameters needed to calculate the activity coefficients of the complexes and the heats of the reactions by which they are formed. These results are sued to calculate tables of recommended values for the solubility of silver chloride in the host solutions as a function of concentration from 0 to 150°C and to make a critical evaluation of the reliability of previously published data.     

Thermodynamic and NMR study of aggregation of dodecyltrimethylammonium chloride in aqueous sodium salicylate solution

The complex aggregation processes of dodecyltrimethylammonium chloride (DTAC) have been studied in dilute solutions of sodium salicylate (NaSal) by isothermal titration calorimetry and electrical conductivity at temperatures between 278.15 K and 318.15 K. A structural transformation that was dependent on the concentrations of DTAC and NaSal was observed. The micellization process in dilute solutions of DTAC has been subjected to a detailed thermodynamic analysis and shown to occur at considerably lower critical micelle concentrations than reported for DTAC in water and NaCl solutions. Gibbs free energy, Δ _mic G ^o, and entropy, Δ _mic S ^o, were deduced by taking into account the degree of micelle ionization, β, estimated from conductivity measurements. From the temperature dependence of the enthalpy of micellization, Δ _mic H ^o, the heat capacities of micellization, D_mic c_p^o {\Delta_{{{\rm mic} }}}c_p^o were determined and discussed in terms of the removal of large areas of non-polar surface from contact with water upon micellization. The process is exothermic at all temperatures, indicating, in addition to the hydrophobic effect, the presence of strong interactions between surfactant and salicylate ions. These were confirmed by ¹H NMR spectroscopy and diffusion NMR experiments. Salicylate ions not only interact with the headgroups but also insert further into the micelle core. At c _NaSal/c _DTAC > 2.5, the structural rearrangements occur even at relatively low concentrations of NaSal.     

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.     

Thermodynamic and structural properties of aqueous linear diol solutions

Thermodynamic characteristics of aqueous linear diol solutions are calculated. These data are used to identify regularities in the variations of the structural properties of the mixtures being studied. The correlation between the entropy and enthalpy characteristics of water-diol systems with excess packing coefficients is evidence that the structural and energy properties of aqueous linear diol solutions are determined by universal interactions. The form of the concentration dependences of the solvation enthalpies and entropies of noble gases in water-linear diols mixtures is determined by the reorganization component and is attributed to the destruction of the H bond network of water, which results in the formation of the most densely packed solutions in the medium range of compositions.     

Enthalpies of reaction of calcium chloride and sodium oxalate in an aqueous NaCl solution

The heats of mixing of dilute aqueous solutions of calcium chloride and sodium oxalate with additions of 1–5 wt % NaCl at 298.15 K and the heats of dilution of calcium chloride solutions were measured. Increasing the sodium chloride content in a solution noticeably increases the time of precipitation of calcium oxalate. A fine precipitate of CaC₂O₄ formed in solutions containing 3 and 5 wt % NaCl is difficult to remove from the parts of a calorimeter cell. The enthalpies of precipitation of CaC₂O₄ depend slightly on the content of the “background electrolyte,” whereas the enthalpies of dilution, owing to ion association, significantly decrease in magnitude and become positive in a 5% NaCl solution. The “standard” enthalpy of precipitation in water, determined by extrapolation of the experimental values to the zero concentration of the background electrolyte, differs noticeably from the enthalpy of precipitation in water.     

Coacervation of copolymer of diallyldimethylammonium chloride and sodium styrenesulfonate aqueous solution

Coacervate behavior of polyelectrolyte complexes has been studied by many papers. Few studies have focused on the coacervate behavior of amphoteric polymer. In this study, amphoteric copolymer of diallyldimethylammonium chloride (DM) and sodium styrenesulfonate (SS) (the copolymer was noted as DMS) was synthesized with the mole content of SS to DM ranged from 0 to 10%. Firstly, DMS was characterized by static light scattering, FTIR, ¹H-NMR, TGA and DSC. Then, its phase and coacervate behaviors were studied. Turbidity was utilized as an indicator for the coacervate formation. It was found that when the SS content was more than 4 mol%, DMS coacervate would be formed in deionized water at a certain concentration. Temperature and pH have no effect on the formation of DMS coacervate. Meanwhile, salts has a great influence on the DMS coacervation. Unlike the results of the other polyelectrolyte complexes, Na₂SO₄, Na₂HPO₄, NaCOOCH₃, sodium citrate and NaI cannot prevent the DMS coacervate formation. However, the addition of NaCl, NaNO₃, NaBr and NaSCN can prevent the coacervate formation. The influence cannot be described by Hofmeister-like behavior. Results of surface tension and fluorescence spectrum presented that the driving forces to formation of DMS coacervate are the electrostatic interaction and the intermolecular hydrophobic interaction.     

Helium diffusion in aqueous sodium chloride solution at high pressures

A molecular dynamic investigation of self-diffusion coefficients of helium and water in aqueous NaCl solution is performed. To understand the nonlinear behavior of the self-diffusion coefficients, a number of structural characteristics (radial distribution functions, hydrogen bond network topology) are calculated. The electrolyte concentration range is discussed in which a local increase in helium self-diffusion coefficient is observed. It is shown that this behavior is caused by a breakdown of the network of hydrogen bonds due to competition between ion positions in the states of solvent-separated and contact pairs.     

Thermodynamic properties of the benzene-phenol dimer in dilute aqueous solution

Precise vapor pressure-solubility measurements have been obtained for dilute solutions of benzene and phenol in water at 15, 25, 35 and 45°C. All of the results are consistent with a mass action model that attributes deviations from ideal solution behavior to the formation of benzene dimers and hetero-dimers between benzene and phenol. The benzene-phenol dimer forms endothermically at 25°C, with a very large negative heat capacity, and a formation constant that reaches a maximum value of 0.66 l-mol^?1 at approximately 35°C. Thermodynamic properties of the benzene-phenol dimer are reported and compared with those of other aggregates that are believed to be stabilized primarily by hydrophobic interactions.     

Thermodynamic study of metabolic reactions in an aqueous protein solution

Summary The time dependences of the thermal power of aqueous myoglobin solutions were measured by microcalorimeter at 298.15 K. Exothermic reactions occurred in aqueous myoglobin solutions due to the metabolism of aerobic microbes, and these roughly consisted of four phases. The generation times obtained were about (55±5) min for the logarithmic exothermal reaction phase. The total energies were considerably dependent on the amount of oxygen present, suggesting strongly that the exothermic reaction was caused by aerobic microbes. The apparent thermal metabolic rates were positively dependent on the concentration of myoglobin, probably because of the effects of myoglobin as a food source and/or as a donor of oxygen.     

Further study of individual ion activities in pure aqueous sodium chloride solution

The e.m.f. values between a chloride electrode and a reference electrode were measured in aqueous NaCl solutions between 10(-5) and 6 m, saturated KC1 and 1M KNO(3) bridges being used. The effect of the various liquid junctions is calculated and discussed. The consistency of the results is inspected, assuming either the MacInnes or the Guggenheim convention. The choice of different reference points for the standardization of the e.m.f.'s and for the activity coefficients is discussed. A comparison is made between the results obtained with an Ag/AgCl electrode of the second kind and a solid membrane chloride electrode.     

Thermodynamic study of aqueous sodium and potassium chloride and chromate systems at the temperature 298.15 K

The solubilities of ( m₁NaCl  + m₂Na₂ CrO ₄)(aq) and ( m₁KCl  + m₂ K ₂CrO ₄)(aq) where m denotes molality have been investigated at the temperature T =  298.15 K by the physico-chemical analysis method. Only the crystallization of the simple salts NaCl, Na ₂CrO ₄·4H ₂O, KCl, and K ₂CrO ₄have been established. The ternary solutions have been simulated thermodynamically at T =  298.15 K using the Pitzer model. The necessary thermodynamic parameters (binary and ternary ion-interaction parameters, thermodynamic solubility products) have been calculated and the theoretical solubility isotherms plotted. A very good agreement is found between calculated and experimental solubility isotherms. The standard molar Gibbs energies of formationΔ_rG_m^o of solid phases crystallizing in the systems under consideration have been estimated from theory.     

Thermodynamic and structural characteristics of aqueous alkanolamine solutions

Journal of Structural Chemistry - Thermodynamic characteristics are calculated for aqueous alkanolamine solutions that are obtained by substituting alkyl radicals for the protons in the amino group...     

Thermodynamic and structural characteristics of aqueous diamine solutions

Thermodynamic characteristics are calculated for aqueous diamine solutions prepared by substituting an amino group for the hydroxyl group of amino alcohols. Patterns are revealed in the change of the structural properties of the mixtures. The correlation between the entropy and enthalpy characteristics of the water–diamine systems and the excess packing coefficients suggests that the universal interactions determine the structural and energy properties of aqueous solutions of the studied diamines. The form of the concentration dependences of the structural and thermodynamic characteristics in the studied systems is found to be symbatic with the data for the mixtures of water with aprotic amides. The reasons for this are discussed by comparing the results with our previously published data for aqueous solutions of aprotic amides.     

Thermodynamic properties and solution equilibria of aqueous bivalent transition metal nitrates and magnesium nitrate

Osmotic coefficients for Mn(NO₃)₂, Co(NO₃)₂, Ni(NO₃)₂, Cu(NO₃)₂, Zn(NO₃)₂, and Mg(NO₃)₂ in aqueous solution have been determined by the isopiestic method at 25°C, and activity coefficients have been derived. The results agree with the literature data for Zn(NO₃)₂, while they are significantly different for Co(NO₃)₂, Cu(NO₃)₂, and Mg(NO₃)₂, and those for Mn(NO₃)₂ and Ni(NO₃)₂ are new. The concentration dependence of the osmotic coefficients for the bivalent metal nitrates is similar to that for the trifluoroacetates, while it differs from those for the other salts of the same series of metals. The results are discussed in terms of the inner-sphere and outer-sphere association of ions, auxiliary information being derived from the concentration effects in the visible spectra of the coloured metal nitrates.     

Thermodynamics of sodium maleate and chloride adsorption at an aqueous solution-gas interface

Surface tension of solutions of sodium chloride in water and sodium maleate in aqueous alkaline solutions in a wide concentration range at 298 and 303 K are measured. It is found that the dependences of surface tension of electrolyte solutions on concentration have extreme character. The obtained dependences are discussed from the standpoint of the effect of the nature of the solute and the processes of desolvation on the composition of surface layers and the surface activity of a solution. Total electrolyte adsorption isotherms are calculated using experimental surface tension and excess adsorption isotherms.     

Effect of structural variation within cationic azo-surfactant upon photoresponsive function in aqueous solution

The cationic azo-surfactants possessing different spacers and tail alkyl chain lengths have been synthesized by azocoupling ofp-alkylaniline orop-ethoxyaniline with phenol, followed by alkylation and quaternalization with dibromoalkane and trimethylamine, respectively. These surfactants showed a good solubility in water. A reversibletrans-cis isomerization of the azosurfactants by photoirradiation was assessed by UV-Vis absorption spectra. Due to a difference in HLB between thetrans- andcis-surfactants, the observed critical micelle concentration (CMC) values and the electric conductivity of the surfactant solution at above the CMC were significantly affected by the photoinducedtrans-cis isomerization. The azo-surfactants bearing moderate alkyl chain lengths such as surfactants 6 (R₂=C₂H₄, R₃=C₄H₉) and 9 (R₂=C₄H₈, R₃=C₂H₅) were found to be effective to achieve large CMC changes (3.6 mmol/L for 6 and 5.9 mmol/L for 9) by UV-light irradiation. The replacement of the tail chain species also affected the photoresponsive function. The surfactant 12, possessingp-ethoxy group as the tail chain, was found to form a stable micelle aggregation as compared with the structurally related surfactant 10 having ethyl unit as its tail group, but it exhibited a large CMC change (5.3 mmol/L) by UV-light irradiation.     

Enthalpies of reaction of calcium chloride and sodium oxalate in aqueous solution of Tween 80

The heats of mixing of dilute calcium chloride and sodium oxalate solutions in water and aqueous solutions of a nonionogenic surfactant, namely, polyoxyethylene (20) sorbitan monooleate (Tween 80) containing 1–5 wt % of the dissolved substance were measured at 298.15 K. The heats of dilution of calcium chloride solutions were determined, and the enthalpies of precipitation of calcium oxalate in water and surfactant solutions were calculated. The surfactant concentration was found to have almost no effect on the enthalpies of the processes under study; rather, it modifies the shape of the resultant deposit by preventing the agglomeration of calcium oxalate particles.     

Structure and physico-chemical properties in mixed aqueous solution of sodium alkvicarboxylate-alkyltrimethylammonium bromide

The physico-chemical properties of organized assemblies (micelle or vesicle ) from sodium alkylcarboxylate - alkyltrimethyl -ammonium bromide mixture have been investigated systematically. In different mixed cationic-anionic surfactant systems, micelles and vesicles can coexist or be transformed into each other on different conditions. The experimental results are explained prelimilarily from the viewpoint of molecular packing geometry. The solubilization of organic compound in the mixed surfactant system was also studied in detail.     

Isopiestic measurements on aqueous mixtures of sodium chloride and strontium chloride

Isopiestic measurements have been made on NaCl–SrCl₂ mixtures at 25°C over the ionic strength range 0.6–6 mole-kg^–1. The results are interpreted in terms of current mixed-electrolyte treatments. The mixing behavior in this system is comparatively simple, but the Pitzer treatment is still clearly superior to the other treatments.