Apparent molar volumes of alkaline earth hexacyanocobaltates (III) in aqueous solution at 25°C

The apparent molar volumes of Mg, Ca, Sr, and Ba hexacyanocobaltates (III) have been determined from 1×10⁴ to 0.2M (mol-dm^–3), using both vibrating tube densimeter and dilatometric methods. The semiempirical Pitzer equation has been used to reproduce the experimental data. Positive deviations from the Debye-Hueckel limiting law (DHLL) have been observed at C<0.01M and are compared with the predictions of two other electrostatic approaches, the DHLL+B₂ approximation of the Mayer theory and the numerical integration of the exponential Poisson-Boltzmann equation. A least squares procedure has been used to obtain the best fit parameters, including the apparent molar volume at infinite dilution.     

Partial molar volumes of tetraalkylammonium hydroxides in aqueous solution at 25°C

The densities of aqueous solutions of tetramethylammonium, tetraethylammonium, tetra-n-propylammonium and tetra-n-butylammonium hydroxide have been measured at 25°C in the concentration range 0.1–1.0 mol-kg^-1 . The apparent and partial molar volumes are calculated from the density measurements. The apparent molar volumes of the solutes show considerable deviation from the Debye-Hülckel limiting law, even at high dilution. The relation for the concentration dependence of the apparent molar volume is given in an analytical form. The limiting apparent molar volumes of the solutes are split into their ionic components by an extrathermodynamic approach and are discussed in terms of ion-solvent interactions. In this way, the limiting partial molar ionic volume for the hydroxide ion is found to be 2 cm³-mol^-1.     

H2O−D2O solvent isotope effect in the volume behavior of some high-charge high-size electrolytes

The apparent molar volumes V of KCl, BaCl₂, K₂SO₄, LaCl₃, Co(en)₃Cl₃ [Tris(ethylenediamine)cobalt(III) chloride], K₃Co(CN)₆, K₃Fe(CN)₆, K₄Fe(CN)₆, and Ba₃[Co(CN)₆]₂ have been determined at 25°C in both light and heavy water. The V values in D₂O are systematically lower and increase more rapidly with salt concentration than the V in H₂O. The volume of transfer from H₂O to D₂O as well as the partial molar volume at infinite dilution in both solvents have also been calculated. These results together with literature values for other electrolytes were used to estimate both of these quantities for D₂O solutions of individual ions. The predictions of ion hydration models and ion-ion interactions are compared with experimental observations.     

Hydration behavior of mixed ligand chromium complexes. Part I: partial molar volumes and partial molar adiabatic compressibilities of oxalato and mixed oxalato — Ethylxanthato chromate(III) complexes

Densities and ultrasonic velocities in aqueous solutions of cis-K[Cr(ox)₂(H₂O)₂], K₃[Cr(ox)₃] and KSSCOC₂H₅ and a mixed ligand complex K₂[Cr(ox)₂SSCOC₂H₅], where SSCOC₂H₅ is the ethylxanthate ligand, have been measured at 25, 35 and 45°C. Limiting partial molar volumes, partial molar adiabatic compressibilities and hydration numbers of the complex salts as well as of the ligand have been calculated. The implication of the findings are discussed.     

Partial molar volumes of selected gases in some ionic liquids

The partial molar volume of a gas that is dissolved at high dilution in a solvent is required to express the influence of pressure on Henry's constant as well as to describe the volume change (expansion) of the liquid caused by the dissolved gas. The correlations of recently published experimental results for the solubility of some selected gases (CO₂, Xe, CH₄, CF₄, H₂, CO, O₂) in three imidazolium-based ionic liquids (1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]), 1-n-butyl-3-methylimidazolium methyl sulfate ([bmim][CH₃SO₄]), and 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf₂N])) determined by the synthetic method were re-evaluated by also considering the experimentally determined volumetric properties. The new evaluation does not change the published results for Henry's constants, but additionally yields reliable information on the partial molar volume of those gases in the mentioned ionic liquids at temperatures from about 293 to 413 K.     

Thermodynamics of concentrated electrolyte mixtures. II. Densities and compressibilities of aqueous NaCl−CaCl2 at 25 °C

Densities and ultrasonic velocities of NaCl–CaCl₂ aqueous mixtures at 25 °C have been measured for the ionic strength range I=0.30–20.0. Where NaCl solubility permitted, both properties were measured over the range of compositions from pure NaCl to pure CaCl₂ at constant I. Apparent molar volumes and apparent molar compressibilities of the mixtures were calculated. The Pitzer form of the specific interaction theory is used to predict the properties of the binary mixtures from the properties of the single salt solutions. It provides a good fit over the full range of ionic strength for apparent molar volumes but a much inferior fit for compressibilities. It is also clear that in the high ionic strength range, explicit mixing parameters must be included for an excellent fit.     

Reaction volume of protonic ionization for buffering agents. Prediction of pressure dependence of pH and pOH

Reaction volumes V^o at infinite dilution and 25°C are obtained by use of a Hashitani dilatometer for protonic ionizations of buffering agents. Combined with recent finding by Hamann that the pressure dependence of the activity coefficient can be estimated by the limiting Debye-Hueckel law even at high ionic strength, one can predict the pH and pOH for these buffer solutions at high pressure.     

Partial molar volumes of 18-crown-6 ether in organic solvents at 25°C

The partial molar volumes at infinite dilution of 18-crown-6 ether (CE) in a variety of polar and polarizable solvents with molar volumes ranging from 18 to 170 cm³-mol^–1, were measured at concentrations ranging from 0.02 to 0.1 mol-L^–1 at 25°C. The partial molar volumes of the solute at infinite dilution showed remarkable dependancy on the molar volume of the solvent. The partial molar volumes at infinite dilution for the CE increases as the solvent molar volume increases.     

Partial molar volumes and partial molar adiabatic compressibilities of ethylenediamine complexes in water

Densities and ultrasonic propagating velocities of aqueous solutions of ethylenediamine complexes [Co(en)₃]Cl₃, [Cr(en)₃]Cl₃, [Ni(en)₃]Cl₂, and [Cu(en)₂]Cl₂ (en=ethylenediamine), as well as the ligand ethylenediamine were measured at 25°C. The infinite dilution values of the partial molar volume V ₂ ⁰ and partial molar adiabatic compressibility K _s ⁰ were evaluated. The value of K _s ⁰ of the ligand ethylenediamine is nearly zero. The values of V ₂ ⁰ and K _s ⁰ are combined with other interaction parameters, such as the Stokes radii and the viscosity B-coefficients, and their dependece upon the charge number and the stereochemistry of the complex ions is discussed.     

Apparent molar volumes of crown ether complexes in several solvents at 25°C. An estimation of ionic electrostriction

The apparent molar volumes of equimolar concentrations of 18-crown-6-ether (CE) or dibenzo-18-crown-6-ether (B₂CE) and MCl (M=Na, K, or Cs) or MI in dilute solutions of anhydrous methanol, acetonitrile and dimethylsulfoxide have been calculated from density data measured at 25°C. After extrapolation to infinite dilution these results together with the apparent molar volumes of the crown ethers and the alkali metal halides were used to calculate the limiting partial molar volume change for the formation of the complexes. By noting that the charge of the complexed cation has been shown to be completely shielded from the solvent, the volume of complexation can be assumed to be a good estimation of the volume change due to electrostriction of the solvent by the cationic charge. The results are compared to the predictions of the Hepler equation.Presented at the Symposium on Electrochemistry and Spectroscopy of Solutions, Honoring Johannes Coetzee, University of Pittsburgh, November 30, 1989.On leave from Rhodes University, Grahamstown, South Africa.     

An efficient palladium catalytic system for microwave assisted cyanation of aryl halides

Application of a new catalytic system for cyanation reaction of various aryl halides using K₄[Fe(CN)₆] as cyanating source was examined. The reactions were performed under microwave irradiation and results showed that application of this catalytic system and DMF at 130 °C minimized the reaction times from hours to minutes in good to excellent yields.     

Apparent molar volumes and compressibilities of selected electrolytes in dimethylsulfoxide

Densities at T = (293.15, 298.15, 303.15, 313.15, 323.15, and 333.15) K and sound velocities at T = 298.15 K of tetraphenylphosphonium bromide, sodium tetraphenylborate, sodium bromide, and sodium perchlorate in dimethylsulfoxide have been measured over the composition range from (0 to 0.3) mol · kg⁻¹. From these data, apparent molar volumes and apparent molar isentropic compressibilities at infinite dilution as well as the expansibilities have been evaluated. The results have been discussed in terms of employing tetraphenylphosphonium tetraphenylborate as a reference electrolyte in splitting the limiting apparent molar volumes and apparent molar isentropic compressibilities into ionic contributions.     

Partial molar volumes of monovalent ions in ethanolamine and water + ethanolamine mixtures at 25°C

Precise densities for sodium of chloride, bromide and iodide and potassium iodide in ethanolamine and water+ethanolamine mixtures (15, 30, 50, 60, 70, 80 and 90 mass% ethanolamine) up to a maximum salt molality of 0.15 mol-kg⁻¹ are reported from measurements at 25°C using a vibrating tube densimeter. The electrolyte apparent molar volumes were calculated and extrapolated to infinite dilution using the Masson equation to yield the limiting electrolyte partial molar volumes. The limiting ionic partial molar volumes V _ion ^o were estimated using Mukerjee's method. A correspondence principle proposed earlier for predicting ionic entropies could be used for the estimation of V _ion ^o for rubidium and cesium salts. The estimates of the contributions from geometric and the electrostrictive effects to V _ion ^o are also reported. The variations in these contributions with the change in solvent composition are discussed in terms of the changes in the solvent structure.     

Excess enthalpies and apparent molar volumes of aqueous solutions of crown ethers and cryptand(222) at 25°C

The enthalpies of dilution and densities of aqueous solutions of 12-crown-4, 15-crown-5, 18-crown-6, 1,10-diaza-18-crown-6 and cryptand (222) were measured at 25°C. The excess enthalpies and enthalpic coefficients of solute-solute interactions were calculated by the McMillan-Mayer theory formalism. Values for the apparent molar volumes at infinite dilution were determined by extrapolation. The contributions of the-CH₂CH₂O-group to values of h₂ and to the limiting partial molar volume were calculated for the series of crown ethers studied. It is concluded that the hydrophobic hydration and the hydrophobic solute-solute interaction are predominant in the solutions investigated.     

Chemiluminescence of CdTe quantum dots using K3Fe(CN)6 as oxidant and its capping ligand-dependent effect

Water-soluble CdTe quantum dots (QDs) capped with three different thioalkyl acids (mercaptoacetic acid, cysteine and glutathione) were synthesized in aqueous solution. In basic media, K₃Fe(CN)₆ could directly oxidize the water-soluble CdTe QDs to produce strong CL emission. It was found that the CL intensity depended on the capping ligand and size of CdTe QDs. CL spectra and fluorescence spectra of the system were measured to investigate the CL reaction mechanism. Moreover, the effects of 17 metal ions on the CL system were carefully investigated. Ca²⁺, Co²⁺, Mn²⁺, Hg²⁺, Mg²⁺, Cu²⁺, Ni²⁺, Cr³⁺ and Fe³⁺ could markedly inhibit the CL signal of the K₃Fe(CN)₆–CdTe QDs system, which makes it applicable for the detection of such ions. This work is of importance for gaining a better understanding of the unique optical and physical chemistry properties of QDs, and it is also helpful to find more practical applications of QDs.     

Partial molar volumes of cryptand-222 in organic solvents at 25°C

The partial molar volumes at infinite dilution of cryptand-222 (C-222) in water, methanol, acetonitrile, ethanol, dimethylsulfoxide, propanol, 2-propanol, chloroform, benzene, 1-butanol, cyclohexane, butyl-methylketone, hexane, tetrahydronaphthalene, heptane, octane, cyclohexylbenzene and decane were measured at concentrations ranging from 0.01 to 0.1 mol-L^–1 at 25°C. The partial molar volumes at infinite dilution showed remarkable dependency on the molar volume of the solvent. The partial molar volumes at infinite dilution for C-222 increase as the solvent molar volume increases.     

Thermodynamics of aqueous EDTA systems: Apparent and partial molar heat capacities and volumes of aqueous strontium and barium EDTA

Apparent molar heat capacities and volumes have been determined for Na₂SrEDTA (aq) and Na₂BaEDTA (aq). Standard state partial molar heat capacities and volumes have been calculated as well as the partial molar properties at 0.1 m ionic strength that are needed for various thermodynamic calculations. Selected enthalpies and stability constants from the literature have been combined with out heat capacities to generate predicted stability constants to 200°C.     

Relative partial molar enthalpies and apparent molar volumes of dipeptides in aqueous solution

Enthalpies of dilution at 25°C of aqueous solutions of the dipeptides glycylglycine, glycylalanine and alanylalanine have been determined and used to calculate the partial molar enthalpies of the solvent water in the solutions. The partial molar volumes of these dipeptides are also reported. The results are discussed in terms of the likely solute-solvent interactions.     

Volumetric properties of ascorbic acid (vitamin C) and thiamine hydrochloride (vitamin B1) in dilute HCl and in aqueous NaCl solutions at (283.15, 293.15, 298.15, 303.15, 308.15, and 313.15) K

Apparent molar volumes and apparent molar isentropic compressibilities of ascorbic acid (vitamin C) and thiamine hydrochloride (vitamin B₁) were determined from accurately measured density and sound velocity data in water and in aqueous NaCl solutions at (283.15, 293.15, 298.15, 303.15, 308.15, and 313.15) K. These volume and compressibility data were extrapolated to zero concentration using suitable empirical or theoretical equations to determine the corresponding infinite dilution values. Apparent molar expansibilities at infinite dilution were determined from slopes of apparent molar volume vs. temperature plots. Ionization of both ascorbic acid and thiamine hydrochloride were suppressed using sufficiently acidic solutions. Apparent molar volumes at infinite dilution for ascorbic acid and thiamine hydrochloride were found to increase with temperature in acidic solutions and in the presence of co-solute, NaCl. Apparent molar expansibility at infinite dilution were found to be constant over the temperature range studied and were all positive, indicating the hydrophilic character of the two vitamins studied in water and in the presence of co-solute, NaCl. Apparent molar isentropic compressibilities of ascorbic acid at infinite dilution were positive in water and in the presence of co-solute, NaCl, at low molalities. Those of thiamine hydrochloride at infinitive dilution were all negative, consistent with its ionic nature. Transfer apparent molar volumes of vitamins at infinite dilution from water solutions to NaCl solutions at various temperatures were determined. The results were interpreted in terms of complex vitamin-water-co-solute (NaCl) interactions.     

Vapor–liquid equilibria and excess molar volumes of diethylamine(1) + acetone(2) and diethylamine(1) + acetonitrile(2) binary systems

Isothermal vapor–liquid equilibrium (VLE) data for diethylamine(1)+acetone(2) and diethylamine(1)+acetonitrile(2) binary systems were obtained at 323.15 K by dynamic method. Excess molar volumes at 298.15 K for these systems were measured by a dilution dilatometer. VLE data have been checked for thermodynamic consistency and correlated by Wilson, NRTL and UNIQUAC equations. UNIFAC group interaction parameters for CH₂NH---CH₃CO and CH₂NH---CH₃CN pairs are also obtained from the experimental VLE data.