Search

The three-parameter extended Hückel equations with parameters B, b1, and b2 have recently been successfully tested against existing vapor pressure, electrochemical, and solubility data for aqueous NaCl solutions at temperatures from (273 to 373) K (Partanen and Partanen in J. Chem. Eng. Data 65:5226–5239, 2020). In the present study, we extend this model to the apparent and partial molar enthalpy data of these solutions. The enthalpy equations were determined using a new calculation method that gives practically the same results as that used in another previous study (Partanen et al. in J. Chem. Eng. Data 62:2617–2632, 2017), but the new method is much simpler. In the previous enthalpy study, dilute NaCl solutions up to m = 0.2 mol⋅kg−1 were considered in the range from T = 273 to 353 K. Following the success of the three-parameter extended Hückel model within the whole concentration range at various temperatures, we tabulate new values for relative apparent and partial molar enthalpies for NaCl solutions at rounded molalities. The resulting values are extensively tested against the literature ones. The best agreement is obtained for temperatures below 288 K and between 313 and 353 K. Elsewhere, at least a reasonable agreement is obtained. As no enthalpy or heat capacity data were used in the estimation of our model's parameters and as the model has excelled in explaining other high-precision thermodynamic data, we argue that the recommended enthalpy values should be preferred even for the temperatures where the agreement is only reasonable due to potential problems associated with the literature values. These problems are also considered in the study. [ABSTRACT FROM AUTHOR]

The pressure dependences of the osmotic and activity coefficients of lithium nitrate (LiNO3) in ethanol at 298.15 K up to 40 MPa and 3.0 mol·kg−1 have been estimated from literature volumetric data on LiNO3 solutions in ethanol using the Pitzer ion-interaction or virial coefficient approach. In particular, the volumetric Pitzer ion-interaction parameters ( β MX 0 V , β MX 1 V , and C MX V ) have been evaluated from a mathematical fit of literature apparent molar volume data to the appropriate Pitzer equation. These were then expressed as polynomials in pressure, which were used to calculate the change in the osmotic and activity coefficients in going from an initial pressure of p1 to a final pressure of p2. These pressure dependences have subsequently been coupled with the osmotic and activity coefficient values of ethanolic LiNO3 solutions at atmospheric pressure obtained from the literature to yield a comprehensive set of osmotic and activity coefficients for LiNO3 solutions in ethanol at 298.15 K, pressures of 5, 10, 15, 20, 25, 30, 35, and 40 MPa, and molalities to 3.0 mol·kg−1. The approximation as to the pressure dependence of the dielectric constant of ethanol estimated using the isothermal compressibilities has been tested for pressures above 0.1 MPa. The results demonstrate that this approximation becomes poorer with the increase in pressure as far as ethanol is concerned. [ABSTRACT FROM AUTHOR]

Densities of binary mixtures of polar organic solvents with alcohols were measured at 25‡C. The solvents studied were N,N-dimethylformamide, dimethylsulfoxide, and formamide while alcohols were butanol, pentanol, hexanol, and 1,4-butanediol. Density measurements of hydrocarbons (from pentane to dodecane and some heptane isomers) + N,N-dimethylformamide were also performed. From these data the apparent molar volumes of alcohols and hydrocarbons as functions of concentration were calculated. The standard partial molar volumes were obtained by extrapolation to infinite dilution and are discussed in terms of group contributions. [ABSTRACT FROM AUTHOR]

The solubilities of some univalent potassium salts (KF, KCl, KBr, KI, KClO, KSCN, and KCNO) in propylene carbonate (PC) were determined at different temperatures from (25.0 to 45.0) °C through flame emission spectroscopy. From the solubility measurements, the thermodynamic parameters ∆ G, ∆ H and ∆ S of solution were calculated. Measurements were carried out via electrical conductimetry and FTIR to investigate the formation of ion pairs and the ion-solvent interactions. This study was motivated by the open question of whether specific ion (Hofmeister) effects are related to the structure of the solvent (i.e., hydrogen bonding). As for water, these effects are due to solute-induced solvent structure changes not accounted for by electrostatic forces. [ABSTRACT FROM AUTHOR]

In this paper density, sound velocity, and refractive index for the binary system (butyric acid + hexanoic acid) were measured over the entire composition range and at 5 K intervals in the temperature range 293.15-313.15 K. The excess molar volumes, isentropic compressibilities, excess isentropic compressibilities, deviation in refractive indices, molar refractions, and deviation in molar refractions were calculated by using the experimental densities, sound velocities, and refractive indices, respectively. The Redlich-Kister equation was used to fit the excess molar volume, excess isentropic compressibility, deviation in refractive index and deviation in molar refraction data. The Lorentz-Lorenz approximation was used to correlate the excess molar volume from the deviation in refractive index and also to predict the density from refractive index or the refractive index from density of the binary mixtures. Four sound velocity mixing rules were tested and the best model for the systems studied in this work was the Berryman mixing rule. The thermodynamic properties are discussed in terms of intermolecular interactions between the components of the mixtures. [ABSTRACT FROM AUTHOR]

The diffusion properties at two overall compositions of a ternary aqueous system containing α-cyclodextrin and a double-functional guest molecule, namely di- tert-butyl l-tartrate, have been studied by means of the Gouy interferometry. The experimental data are interpreted in terms of two independent chemical equilibria involving inclusion compounds. The elements of the diffusion coefficient matrix have been expressed as functions of the two equilibrium constants as well as of the diffusivities of the actual species occurring in solution. The reliability of the diffusion coefficients obtained through the Fujita-Gosting-Revzin procedure is also discussed in terms of its dependence on the composition of solutions used in the Gouy experiments. [ABSTRACT FROM AUTHOR]

This work analyzes the temperature dependence of the only fitting parameter of the SIT (Specific Ion Interaction Theory) model for activity coefficients. Relations based on the so-called 'primitive' model for the inter-ionic potential suggest that the binary interaction parameter is proportional to the pure water density. In order to check this correlation, activity coefficients and related data are tested for twenty 1:1 electrolytes, where the necessary data are available at temperatures up to at least 523 K. A strong correlation with water density is universally observed at temperatures T > 360 K (or water densities, $$ \rho_{1}^{*} $$ , below 950 kg·m). In accordance with expectations from theoretical considerations, at these temperatures and water densities, the SIT parameter is constant under isochoric conditions (a constant water density), and decreases with decreases of $$ \rho_{1}^{*} $$ . Over the whole temperature range, usually between 273 and 573 K, the temperature and water density dependence of the SIT model interaction parameters, $$ \varepsilon_{\gamma } (M,X) $$ , where M stands for a cation and X for an anion, is well described (including data at pressures up to 100 MPa) by the following expression $$ \varepsilon_{\gamma } (M,X) = b_{0} + b_{1} \rho_{1}^{*} + \frac{{b_{2} }}{T - 210} $$ . [ABSTRACT FROM AUTHOR]

Excess molar volumes V for 40 mixtures of heptane with a liquid alkane and apparent molar volumes in heptane for eight solid alkanes have been obtained at 298.15 K. They include five linear, 30 branched-chain, and 13 cyclic alkanes. Almost all systems exhibit negative V values. For mixtures with open chain alkanes, V increases from C5 to C7 and then decreases. A similar trend is shown by mixtures with cycloalkanes. V values are compared with known H data for mixtures with heptane and tetrachloromethane. Signs and trends of V and H are correlated with the free volume and interactional terms of the Flory theory. The partial molar volumes at infinite dilution in heptane, V°, have also been obtained and discussed together with literature data on other hydrocarbons and polar compounds. The calculated contributions to V° by CH, CH, CH and C groups are compared with previously determined contributions of polar groups. The lower contributions of the latter groups are explained with the volume contraction caused by dipole-induced dipole interaction. The volume effects associated with branching and cyclization have been evaluated and compared with the corresponding effects on solvation enthalpy. The branching effect, in the order of magnitude of few cm·mol, and the larger negative values of cyclization volumes, down to −24 cm·mol, are discussed in terms of packing and solute-solvent interactions, in analogy to polar organic solutes either in heptane and tetrachloromethane. A negative cyclization effect is also exhibited by the solvation enthalpies. [ABSTRACT FROM AUTHOR]

Precise measurements of viscosities and densities of solutions of EtNBF in propylene carbonate are reported in wide range of concentrations from 0.01 to 0.8 mol⋅kg at 283.15, 298.15, 308.15 and 313.15 K. The viscosity data have been analyzed by the Jones-Dole equation for dilute solutions as well as by the Angell equation for concentrated solutions. The activation parameters have been evaluated using the transition-state treatments of Eyring and Feakins. The contributions of volumetric and energetic terms for viscous flow of the EtNBF in propylene carbonate are evaluated. [ABSTRACT FROM AUTHOR]

Abstract  Property data for tetraalkylammonium cations, [H(CH2) n ]4N+, are reviewed. They pertain to the isolated cations and their transfer from the gas phase into aqueous solutions. Various properties of these cations in aqueous and non-aqueous solutions and data for their transfer between these are also reviewed. Emphasis is placed on the dependence of data on the length n of the alkyl chains rather than on the absolute values. Most of the data are available only for the first four members of the series. The properties of the isolated ions increase linearly with the chain length. Molar enthalpies of formation of the gaseous and aqueous cations, and absolute standard molar enthalpies of hydration, are derived. Standard molar entropies of dissolution of several salts in water are obtained from their solubilities and enthalpies of solution. The molar entropies of the crystalline iodides of the first four members of the series then give the standard partial molar entropies of the aqueous cations and their molar entropies of hydration. The standard partial molar volumes in aqueous and non-aqueous solutions are quite linear with n and in non-aqueous solutions the molar volume hardly depends on the nature of the solvent. On transfer from water to non-aqueous solvents the volume of Me4N+ suffers some shrinkage, that of Et4N+ appears to be unaffected, but from Pr4N+ onwards an increasing expansion takes place. This unexpected result is tentatively explained by hydrophobic intra-molecular association of pairs of alkyl chains in aqueous solutions, resulting in a tightening of the structure. The transfer of the R4N+ cations from water into non-aqueous solvents is governed by a large positive entropy change, outweighing the smaller positive enthalpy change. The transport properties of the aqueous R4N+ cations are non-linear with n. A major impediment to movement is thus the sticking of the water molecules to the ice-like hydrophobic hydration sheaths of the larger cations. The number of water molecules affected by the hydrophobic cations is open to widely differing estimates resulting from various approaches, and constitute an open issue. [ABSTRACT FROM AUTHOR]

Abstract   Apparent molar volumes have been determined using a high-pressure vibrating-tube densimeter for aqueous solutions of 2- and 3-hydroxypropionic acid, at temperatures from 100 �C to 325 �C and pressures as high as 15 MPa. The results were corrected for acid ionization and extrapolated to infinite dilution to obtain the standard partial molar volumes, V 2o. The standard partial molar volumes of both isomers increase with temperature towards a positive discontinuity at the critical point, which is typical for almost all non-electrolytes. The temperature dependence of V 2o for the sodium salts of the acids is consistent with a negative discontinuity at the critical point, as displayed by all other aqueous electrolytes. Values of the apparent molar volumes of 2-hydroxypropionic acid are more positive than 3-hydroxypropionic acid by ∼2 cm3⋅mol−1, both in the neutral form and as the sodium carboxylate salt. This is the first demonstration at such high temperatures that functional group additivity in alkyl organic solutes with closely spaced polar groups is preserved to within such small differences. The onset of thermal decomposition prevented measurements at temperatures above 325 �C. [ABSTRACT FROM AUTHOR]

Abstract??The molar conductivities (?) of solutions ofn-tetrabutylammonium tetraphenylborate (NBu4BPh4) in 3-pentanone have been measured in the temperature range from 283.15 to 329.15 K. The conductance data have been analyzed using the Lee-Wheaton conductivity equation with the distance parameter (a) set at Bjerrum?s pairing distance, and the limiting molar conductivities (?o) and the association equilibrium constants (KA) have been derived. The limiting ion conductivities (?_?o) have been evaluated according to the method of Krumgalz. The ?+ovalues have been compared with ?+ovalues calculated from the empirical equation of Gill. The thermodynamic functions, Gibbs energy (?GAo), enthalpy (?HAo) and entropy (?SAo) for the process of ion-pair formation as well as the activation energy of the ionic movement (?H?) have been evaluated. The obtained results are discussed in terms of ion-ion and ion-solvent interactions. [ABSTRACT FROM AUTHOR]

Abstract?? Ultrasound speeds in aqueous binary mixtures of diethylamine (DEA) were measured across the entire composition range at five temperatures between 278.15 and 308.15 K. Isentropic compressibilities, ?S, were calculated from the ultrasound speed and density data. The excess molar isentropic compressions,KS,mE, were estimated and their variation with the mole fraction of the amine were fitted by the Redlich?Kister equation. Excess partial molar isentropic compressions,KS,iE, were then obtained, allowing separation of the role of each component in the mixing process. Interesting insights are gained from the analysis of the temperature and composition dependence ofKS,iE, principally in the water-rich region. A comparison of the limiting values of this property with those of the limiting excess partial molar isobaric expansion,EP,iE,?, previously published, clearly shows the different sensitivity of these two differential thermodynamic properties to the mixing process. The different behavior of the temperature dependence ofKS,iE,?in the systems, water + DEA, and water + 2-diethylaminoethanol (DEEA), are also analyzed and interpreted in terms of changes in the solute configuration, the degree of hydrolysis and solute-solvent interactions. [ABSTRACT FROM AUTHOR]

Abstract?? The heat capacities of aqueous solutions of acetone, 2,5-hexanedione, diethyl ether, 1,2-dimethoxyethane, benzyl alcohol and cyclohexanol at concentrations of 0.1 to 1.0 mol?kg?1were determined at temperatures of 298.15, 423.15, 473.15 and 523.15 K and pressures up to 28 MPa. The measurements were performed at ambient conditions using the commercial Picker differential flow calorimeter and at high temperatures and pressures with a customized Picker type calorimeter constructed at the Blaise Pascal University, Clermont-Ferrand. Standard molar heat capacities were obtained by weighted extrapolation to the infinite dilution limit. The contributions of ?CO?, ?O? and ?OH groups to the standard molar volume and standard molar heat capacity were determined from the newly determined and literature data. The variation of the three oxygen-containing group contributions with temperature and molecular structure is examined qualitatively. [ABSTRACT FROM AUTHOR]

Excess molar volumes, V m E, over the whole composition range for binary mixtures of 1-butanol, 2-butanol, and 2-methyl-2-propanol + 1-octanol, or 2-octanol, or di- n-butyl ether, or n-hexylacetate were determined at 298.15 K from density measurements carried out with a vibrating-tube densimeter. Small V m E values, both positive and negative, are displayed by mixtures containing 1- or 2-octanol, whereas positive and larger values are always found for mixtures containing dibutyl ether and hexylacetate. These results can be justified in terms of H-bonding interactions and/or steric hindrance due to the branched alkyl chains. Partial molar volumes at infinite dilution of the isomeric butanols in the C8 compounds were also calculated from the apparent molar volumes in dilute solution. The solute-solvent interactions and the effects of the local organisation of the solvent around the butanol molecules were discussed using the void and cavity volumes as different estimates of the intrinsic volume of the molecules. The volumetric behavior of butanols seems to be determined by the solute-solvent interactions rather than packaging effects. [ABSTRACT FROM AUTHOR]

High-precision densitometry measurements of solutions of thioxanten-9-one (TX) in 1,4-dioxane, DMSO, toluene, and benzene have been obtained at 293.15, 303.15, 313.15, 323.15, 333.15, and 343.15K. The partial molar volumes of TX ( ) and the corresponding values at infinite dilution ( ) were determined. The partial molar expansibility ( ) of TX at infinite dilution in each solvent is temperature independent. Dynamic electronic polarizabilities of TX in each aprotic solvent were determined by the Singer–Garito approach. These values are in excellent concordance with the theoretical value for TX of 2.611×10−23cm3 estimated here using DFT/B3LYP/6-311++G(d,p). The partial molar volumes of TX at infinite dilution were calculated and interpreted in terms of the Scale Particle Theory (SPT). The solvent influence on the partial molar volume of TX was found to be due mainly to cavity formation and intermolecular dispersion forces. [ABSTRACT FROM AUTHOR]

An inert, flowing autoclave facility was used to investigate the solubility behavior of α-PbO (litharge, tetragonal) in aqueous solutions of morpholine, ammonia and sodium hydroxide between 38 and 260 ∘C. Lead solubilities increased from about 0.4 mmol-kg−1 at 38 ∘C to about 4.5 mmol-kg−1 at 260 ∘C and were relatively insensitive to the concentration and identity of the reagent used to control the pH. The measured lead solubilities were interpreted using a Pb(II) ion hydroxocomplexing model and thermodynamic functions for these equilibria were obtained from a least-squares analysis of the data. A consistent set of thermodynamic properties for the species Pb(OH)+, Pb(OH)2(aq) and Pb(OH)3− was obtained that will permit accurate lead oxide solubility calculations to be made over broad ranges of temperature and alkalinity. [ABSTRACT FROM AUTHOR]

The partial molar isentropic compressibilities at infinite dilution, K∘S,2, have been determined for several tripeptides of the sequence glycyl-X-glycine, where X is one of the amino acids tyrosine, proline, glutamine, aspartic acid, glutamic acid and lysine in aqueous solution at 25 ∘C. These results, along with those for triglycine, were used to estimate the contributions of the amino acid side-chains to the partial molar isentropic compressibilities of polypeptides. Values for K∘S,2 have also been determined for aqueous solutions of the two peptide salts K[glyaspgly] and Na[glyglugly]. The K∘S,2 results for the peptides and their salts have been combined with literature data for electrolytes to calculate the changes in isentropic compressibility upon ionization of the acidic side-chains. The results are compared with those for other carboxylic acid systems. [ABSTRACT FROM AUTHOR]

The densities of binary systems of difurylmethane (DFM) in methanol have been measured with an Anton Parr DMA 4500 vibrating-tube densimeter over the entire composition range at intervals of 5 K in the temperature range between 288.15 and 308.15 K. Excess molar volumes of the mixture, apparent molar volumes of DFM, and excess partial molar volumes of both components have been calculated to provide insight into the intermolecular interaction present in the mixtures investigated. Excess molar volumes have been fitted to a Redlich–Kister equation and they exhibited negative deviations from ideal behavior. Both the apparent molar volume of DFM and excess partial molar volumes of DFM and methanol exhibit a dependence on composition but are less sensitive to temperature. [ABSTRACT FROM AUTHOR]

Abstract Chloride complexation of cobalt(II), nickel(II) and zinc(II) ions has been studied by calorimetry and spectrophotometry in N-methylformamide (NMF) containing 1.0 mol-dm− 3 (n-C4H9)4NClO4 as an ionic medium at 298 K. A series of mononuclear complexes, MCln(2 -n) + (M=Co, Ni and Zn) with n = 1, 3 and 4 for cobalt(II), n = 1 for nickel(II), and n = 1–4 for zinc(II), are formed and their formation constants, enthalpies and entropies were obtained. It revealed that complexation is suppressed significantly in NMF relative to that in N,N-dimethylformamide (DMF) in all metal systems examined. The suppressed complexation in NMF is mainly ascribed to the smaller formation entropies in NMF reflecting that the solvent–solvent interaction or solvent structure in the bulk NMF is much stronger than that in the bulk DMF. Formation entropies, Δ S1o, of the monochloro complex in DMF, dimethyl sulfoxide and NMF are well correlated with the Marcus’ solvent parameter, Δ ΔvSo/R, according to Δ S1o/R = aΔ ΔvSo/R+b. The a value is negative and similar in all metal systems examined, whereas the b value depends on the metal system. When a gaseous ion is introduced into a solvent, the ionic process of solvation is divided into two stages: the ion destroys the bulk solvent structure to isolate solvent molecules at the first stage and the ion then coordinates a part of isolated solvent molecules around it at the second stage. We propose that the a and b values may reflect the changes in the freedom of motion of solvent molecules at the first and second stages, respectively, of the ionic process of solvation. [ABSTRACT FROM AUTHOR]

Abstract Interactions between α-CD and three alkyl trimethyl ammonium bromides, a homologues series of surfactants, in aqueous solutions have been investigated with titration microcalorimetry at 298.15 K. The results are discussed in the light of the amphiphilic interaction and the iceberg structure of water molecules existing around the hydrophobic tail of the surfactant. The stoichiometry of the host–guest complex changes from 1:1 to 2:1, as the number of carbon atoms (n) in the hydrophobic chain, CnH2n+1, increases from 8 to 14. All the complexes are quite stable, with the apparent experiential stability constants being β1 = 2.65 × 103 dm3-mol−1, β2 = 4.85 × 106 dm6-mol−2, β2 = 6.50 × 106 dm6-mol−2, respectively for n = 8, 12, 14. All the complexation processes are shown to be enthalpy driven, and the standard enthalpy effect (−ΔH0) increases while standard entropy change (ΔS0) decreases with elongation of the hydrophobic chain. [ABSTRACT FROM AUTHOR]

Abstract The densities of tetraalkylammonium bromide, R4NBr (R = Et, Pr, Bu, Hex, Hep, Oct), solutions in dimethylformamide have been measured for the composition range (0.05–0.4) mol-kg−1 at 25 ∘C. Apparent molar Vφ and limiting partial molar volumes 2o of the electrolytes have been evaluated. Using the extrapolation values, the limiting partial molar volumes of the tetraalkymammonium ions (io) have been calculated. Analysis of different contributions to the ionic io indicated partial penetration of solvent molecules into the van der Waal’s volume of tetraalkylammonium (TAA) ions. [ABSTRACT FROM AUTHOR]

A platinum-lined, flowing autoclave facility was used to investigate the solubility behavior of nickel(II) oxide (NiO) in deoxygenated ammonium and sodium hydroxide solutions, between 21 and 315°C. Solubilities were found to vary between 0.4 and 400 nmol-kg−1. The measured nickel ion solubilities were interpreted via a Ni(II) ion hydroxo- and ammino-complexing model, and thermodynamic functions for these equilibria were obtained from a least-squares analysis of the data. Two solid phase transformations were observed: at temperatures below 149°C, the activity of Ni(II) ions in aqueous solution was controlled by a hydrous Ni(II) oxide (theophrastite) solid phase rather than by anhydrous NiO (bunsenite); above 247°C, Ni(II) activities were controlled by cubic rather than by rhombohedral bunsenite. [ABSTRACT FROM AUTHOR]

Complexation of K+ by 18-crown-6 ether (18C6) in pure water and in acetonitrile–water mixed solvents containing 0.1 mol-dm− 3 (C2H5)4NCl has been systematically studied by isothermal titration calorimetry (ITC) at 293, 298, and 303 K. The formation constant K of the 1:1 [K(18C6)]+ complex and the complexation enthalpy Δ rH were simultaneously determined from the titration data. The log K and Δ rH(kJ-mol− 1) values at 298 K are 2.04, −26.2 in pure water and 2.23, −25.0; 2.61, −24.2; 2.95, −23.8; 3.48, −21.0; 3.85, −19.4; 4.36, −18.7; and 5.73, −17.0 in the mixed solvents at xAN (mole fraction of acetonitrile) of 0.043, 0.135, 0.258, 0.448, 0.578, 0.759, and 1.0, respectively. The change in heat capacity for the complex formation, Δ C p°, was also determined by the temperature dependence of Δ rH. Whereas the Δ C p° is (57 ± 11) and (63 ± 20) J-mol− 1-K− 1 in pure water and in the solvent mixture at xAN = 0.043, respectively, it decreases with increasing xAN. The Δ C p° values are −(48 ± 11), −(110 ± 25), −(354 ± 40), −(359 ± 24), and −(304 ± 30) J-mol− 1-K− 1 at xAN = 0.135, 0.258, 0.448, 0.578, and 0.759, respectively. The changes in complexation thermodynamics (Δ Δ rG, Δ ΔrH, and Δ Δ r S) are discussed in terms of the corresponding transfer thermodynamics of K+, 18-crown-6, and [K(18C6)]+ upon transferring from water to acetonitrile–water mixed solvents. It was found that hydrophobic solvation of the complex [K(18C6)]+ plays an important role in complex formation occurring in water and in the water-rich mixed solvent. Moreover, changes in solvent structure significantly affect the transfer enthalpy and entropy of each species, i.e., K+, 18-crown-6, and [K(18C6)]+. The observed monotonous changes in the complexation Gibbs energy, enthalpy, and entropy with solvent composition are due to the effective compensation of the Δ trG, Δ trH, and Δ tr S for K+ with those for 18-crown-6 and [K(18C6)]+. [ABSTRACT FROM AUTHOR]

Standard partial molar volumes of ions were obtained from literature data on 1:1 electrolytes in mixtures of propylene carbonate (PC) with acetonitrile (MeCN) and of water (W) with methanol (MeOH) at 298.15 K. The hypothesis was examined that when the solvents in the mixtures do not differ too much in their polarity and/or hydrogen-bonding ability, only negligible preferential solvation occurs in the solvent shell around the ion where electrostriction takes place. Given the solvent-independent intrinsic volume of an ion, the electrostriction, calculated by the shell-by-shell method, permits the examination of this proposition. This hypothesis was indeed validated by the calculated standard partial molar ionic volumes in the dipolar aprotic mixtures and in the protic aqueous methanol. [ABSTRACT FROM AUTHOR]

The apparent and limiting apparent molar volumes of dilute aqueous solutions of KBF[sub4], and the complexes [Fe(DMSO)[sub6]](BF[sub4])[sub3], [Fe(Py)[sub4](H[sub2]O)[sub2]](BF[sub4])[sub3], [Fe(4-Mepy)[sub2] (H[sub2]O)[sub2]](BF[sub4])[sub3], and [Fe(4-Etpy)[sub2](H[sub2]O)[sub2]](BF[sub4])[sub3] were determined from density data measured at 5, 15, and 25°C. The apparent and limiting apparent molar adiabatic compressibilities of these complexes were determined from ultrasonic sound velocities measured at the same temperatures in dilute aqueous solutions. The volume change associated with complex formation is discussed in terms of the nature of the coordinate bond and also the role of the central metal atom and ligands in the solvation behavior of these complexes. [ABSTRACT FROM AUTHOR]

Densities of dilute solutions of the electrolytes tetraethylphosphonium iodide and tetraethylammonium iodide in the nonaqueous solvents methanol, ethanol, l-propanol, l-butanol, acetonitrile, and 2-propanone were measured at 25°C. Using published values for the Debye-Hückel limiting slopes A[sub v], apparent molar volume data were fitted to the Pitzer equation yielding infinite-dilution partial molar volumes V[sup ∞, sub i] and deviation parameters B[sub v]. It is found that the variation in the van der Waals volume of the cationic central atoms is about one half the experimental volume change in 2-propanone solutions, but twice that value in the other five solvents. This finding is interpreted in terms of openness of solute structure and solvent penetration. Parameter B[sub v] for each salt is shown to be solvent dependent. An interesting approximate linear variation between A[sub v] and B[sub v] parameters is suggested by the data. This empirical relationship would entail correlation of short- and long-range interionic interactions in solution. [ABSTRACT FROM AUTHOR]

A comprehensive array of electrochemical cell measurements for the system HCl +SmCl3 + H2O was made from 5 to 55°C using a cell without liquid junction ofthe type:Pt; H2(g, 1 atm)|HCl ( mA) + SmCl3 ( mB)|AgCl, Ag (A)The present study, unlike previous studies of trivalent ions, are not complicatedby hydrolysis reactions. Measurements of the emf were performed for solutionsat constant total ionic strengths of 0.025, 0.05, 0.1, 0.25, 0.5, 1.0, 1.5, 2.0, 2.5,and 3.0 mol-kg−1. The mean activity coefficients of HCl (γHCl) in the mixtureswere calculated using the Nernst equation. All the experimental emf measurements(about 850) were first treated in terms of the simpler Harned's rule. Harnedinteraction coefficients (αAB and βAB) were calculated. The linear form of Harned'srule is valid for most ionic strengths, but quadratic terms are needed at I = 1.5and 3 mol-kg−1. The Pitzer model was used to evaluate the activity coefficientsusing literature values, β(0), β(1), and Cφ, for HCl from 0 to 50°C and 25°C forSmCl3. The effect of temperature on the parameters for SmCl3 has been estimatedusing enthalpy and heat-capacity data. The mixing parameter ΘH,Sm wasdetermined at 25°C. The addition of the ΨH,Sm,Cl coefficient did not improve the fitsignificantly and no temperature dependence was found to be significant. Thevalue of ΘH,Sm = 0.2 ± 0.01 represented the values of γHCl with a standarddeviation of σ = 0.009 over the entire range of temperatures and ionic strength.The use of higher-order electrostatic effects (EΘH,Sm, EΘH,Sm) was included as itgave a better fit of the activity coefficients of HCl. [ABSTRACT FROM AUTHOR]

Apparent molar volumes and adiabatic compressibilities of 18-crown-6,15-crown-5, 12-crown-4, tetraglyme, and triglyme were measured at 15, 25, and40°C. Apparent molar expansibilities and∂ K∂ Tvalues were also determined.The contribution of the -CH2CH2O- group to the limiting partial molar volumesand compressibilities of cyclic and open-chain ethers are compared. It isconcluded, on the basis of the compressibility results, that there is a subtle differencebetween the hydration of the ethene-oxide group in cyclic and open-chain ethers. [ABSTRACT FROM AUTHOR]

The emf of the cellwithout a liquid junction was used to investigate the HCl + GdCl3 + H2O mixedelectrolyte system. The emf of the cell was measured for HCl + GdCl3 + H2Osolutions at ionic strengths of 0.025, 0.05, 0.1, 0.5, 1.0, 1.5, and 2.0 mol-kg−1and at eleven temperatures ranging from 5 to 55°C at 5°C intervals. The meanactivity coefficients for HCl in the mixtures were determined using the Nernstequation. About 793 experimental emf data points were treated by the Harnedequations. Results show that hydrochloric acid follows Harned's rule at all ionicstrengths, but the quadratic term is needed for I = 1.5 mol-kg−1. Theion-interaction treatment of Pitzer was used to evaluate the results. The binary andternary mixing parameters at 25°C were found to be ΘH,Gd = 0.07 ± 0.03 andΨH,Gd,Cl = 0.14 ± 0.03. These values were determined using literature values ofβ(0), β(1), and Cψ for GdCl3 at 25°C and estimates of the effect of temperaturefrom 5 to 55°C using enthalpy and heat capacity data. [ABSTRACT FROM AUTHOR]

Partial molar volumes at infinite dilution, $$\overline {V^0 } $$ , in water at 25°C for organicelectrolytes and nonelectrolytes are described through a simple additivity schemebased on the intrinsic volume approach. The contributions to $$\overline {V^0 } $$ of hydrocarbongroups were determined from the “experimental” CH2 increment assuming thatall hydrocarbon portions have the same packing efficiency in aqueous solution.Twenty-two charged and 51 uncharged groups, are assigned a $$\overline {V^0 } $$ contribution and the partial molar volumes of nearly 400 monofunctional organic solutes arereproduced with a root mean square of deviation of 0.9 cm3-mol−1. The differentvolumetric behavior of linear, branched, and cyclic molecules is discussed. Acomparison is made of uncharged (hydrocarbon and polar) with charged groups,as well as of groups with small molecules and ions. A relative estimate is givenof the volume effects (cavity formation, hydrophobic hydration, solvent shrinkage,H bonding, and electrostriction) involved in the interaction of hydrophobic andhydrophilic groups with water. Deviations from additivity for mono- andpolyfunctional solutes, including polyelectrolytes, are analyzed in terms of (1) extensionof the hydration cosphere of different polar centers: (2) intramolecular interactionsand their dependence on nature, number, and mutual distance of interactinggroups. The van der Waals volume Vw is extensively used as molecular descriptor.Estimates of Vw for both charged and uncharged groups are presented. [ABSTRACT FROM AUTHOR]

The hydrolysis of trimethyltin(IV) has been studied by potentiometry (H+ -glass electrode) and calorimetry in various salt media (NaNO3, NaCl, KCl, Na2SO4, and NaNO3—NaCl mixtures). The effect of ionic strength on the hydrolysis constants is accounted for by a simple Debye–Hückel type equation and by Pitzer equations. The results allow us to obtain Δ H for hydrolysis and the temperature dependence of the Pitzer parameters. The resulting coefficients can be used to examine the speciation of (CH3)3Sn+ in multicomponent electrolyte solutions, such as natural waters, over a wide range of temperature and ionic strength. [ABSTRACT FROM AUTHOR]